0000950170-24-053926 | 10-Q | XBRL Viewer

Allowance for Doubtful Accounts Included in Accounts Receivable Net (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Allowance for Doubtful Accounts Included in Accounts Receivable Net Detail [Abstract]
Allowance for Doubtful Accounts	$ 2.8	$ 2.4	$ 3.1

EQUITY

3 Months Ended

Mar. 31, 2024

EQUITY

Note 5 – equity

Common Stock

The Company’s common stock trades on the New York Stock Exchange under the symbol, “UTL.”

The Company had 16,167,887, 16,086,230 and 16,116,724 shares of common stock outstanding at March 31, 2024, March 31, 2023 and December 31, 2023, respectively.

Dividend Reinvestment and Stock Purchase Plan - During the first three months of 2024, the Company sold 5,803 shares of its common stock, at an average price of $50.17 per share, in connection with its Dividend Reinvestment and Stock Purchase Plan (DRP) and its 401(k) plans resulting in net proceeds of approximately $291,200. The DRP provides participants in the plan a method for investing cash dividends on the Company’s common stock and cash payments in additional shares of the Company’s common stock.

Stock Plan - The Company maintains the Unitil Corporation Second Amended and Restated 2003 Stock Plan (the Stock Plan). Participants in the Stock Plan are selected by the Compensation Committee of the Board of Directors to receive awards under the Stock Plan, including: (i) awards of restricted shares that vest based on time (Time Restricted Shares); (ii) awards of restricted shares that vest based on performance (Performance Restricted Shares), effective January 24, 2023; or (iii) awards of restricted stock units (Restricted Stock Units). The Compensation Committee has the authority to determine the sizes of awards; determine the terms and conditions of awards in a manner consistent with the Stock Plan; construe and interpret the Stock Plan and any agreement or instrument entered into under the Stock Plan as they apply to participants; establish, amend, or waive rules and regulations for the Stock Plan’s administration as they apply to participants; and, subject to the provisions of the Stock Plan, amend the terms and conditions of any outstanding award to the extent such terms and conditions are within the discretion of the Compensation Committee as provided for in the Stock Plan. On April 19, 2012 and May 1, 2024, the Company’s shareholders approved amendments to the Stock Plan to, among other things, increase the maximum number of shares of common stock available for awards to plan participants.

The maximum number of shares available for awards to participants under the Stock Plan was 677,500 as of March 31, 2024, and was increased on May 1, 2024 to 1,027,500. The maximum number of shares that may be awarded in any one calendar year to any one participant is 20,000. In the event of certain changes in capitalization of the Company, the Compensation Committee is authorized to make an equitable adjustment to the number and kind of shares of common stock that may be delivered under the Stock Plan and, in addition, may authorize and make an equitable adjustment to the Stock Plan’s annual individual award limit.

Time Restricted Shares

Outstanding awards of Time Restricted Shares fully vest over a period of four years at a rate of 25% each year. During the vesting period, dividends on Time Restricted Shares underlying the award may be credited to a participant’s account. The Company may deduct or withhold, or require a participant to remit to the Company, an amount sufficient to satisfy any taxes required by federal, state, or local law or regulation to be withheld with respect to any taxable event arising in connection with an award.

Prior to the end of the vesting period, the Time Restricted Shares are subject to forfeiture if the participant ceases to be employed by the Company other than due to the participant’s death, disability or retirement.

On January 30, 2024, 22,680 Time Restricted Shares were issued in conjunction with the Stock Plan with an aggregate market value at the date of issuance of approximately $1.1 million. There were 59,163 and 64,243 non-vested Time Restricted Shares under the Stock Plan as of March 31, 2024 and 2023, respectively. The weighted average grant date fair value of these shares was $47.72 and $48.02 per share, respectively. The compensation expense associated with the issuance of Time Restricted Shares under the Stock Plan is being recognized over the vesting period and was $1.0 million and $1.1 million for the three months ended March 31, 2024 and 2023, respectively. At March 31, 2024, there was approximately $1.2 million of total unrecognized compensation cost for Time Restricted Shares under the Stock Plan which is expected to be recognized over approximately 2.8 years. During the three months ended March 31, 2024 there were zero Time Restricted Shares forfeited and zero Time Restricted Shares cancelled under the Stock Plan.

Performance Restricted Shares

Outstanding awards of Performance Restricted Shares vest after a performance period of three years based on the attainment of certain goals set by the Compensation Committee at the beginning of the performance period. If goals are met, awards of Performance Restricted Shares may vest fully; if goals are exceeded, awards of Performance Restricted Shares may vest fully and additional shares of common stock may be awarded; if goals are not met, a portion of the Performance Restricted Shares may vest and/or all or a portion of the Performance Restricted Shares may be forfeited. During the performance period, dividends on Performance Restricted Shares underlying the award may be credited to a participant’s account. The Company may deduct or withhold, or require a participant to remit to the Company, an amount sufficient to satisfy any taxes required by federal, state, or local law or regulation to be withheld with respect to any taxable event arising in connection with an award.

Prior to the end of the performance period, the Performance Restricted Shares are subject to forfeiture if the participant ceases to be employed by the Company other than due to the participant’s death, disability or retirement. Initial awards of Performance Restricted Shares were granted January 24, 2023. On January 30, 2024, there were 22,680 Performance Restricted Shares issued under the Stock Plan with an aggregate market value of $1.1 million. There were 43,453

non-vested Performance Restricted Shares under the Stock Plan as of March 31, 2024. The weighted average grant date fair value of these shares was $50.35 per share. The compensation expense associated with the issuance of Performance Restricted Shares under the Stock Plan is being recognized over the vesting period and was $0.2 million and $0.1 million for the three months ended March 31, 2024 and March 31, 2023, respectively. At March 31, 2024, there was approximately $2.2 million of total unrecognized compensation cost for Performance Restricted Shares under the Stock Plan which is expected to be recognized over approximately 2.3 years. During the three months ended March 31, 2024 there were zero Performance Restricted Shares forfeited and zero Performance Restricted Shares cancelled under the Stock Plan.

Restricted Stock Units

Non-management members of the Company’s Board of Directors (Directors) may elect to receive the equity portion of their annual retainer in the form of Restricted Stock Units (RSU). Restricted Stock Units earn dividend equivalents and will generally be settled by payment to each Director as soon as practicable following the Director’s separation from service to the Company. The Restricted Stock Units will be paid such that the Director will receive (i) 70% of the shares of the Company’s common stock underlying the restricted stock units and (ii) cash in an amount equal to the fair market value of 30% of the shares of the Company’s common stock underlying the Restricted Stock Units. The equity portion of Restricted Stock Units activity during the three months ended March 31, 2024 in conjunction with the Stock Plan is presented in the following table:


Restricted Stock Units (Equity Portion)
	Units		Weighted Average Stock Price
Restricted Stock Units as of December 31, 2023		33,375	$	42.73
Restricted Stock Units Granted		—	$	—
Dividend Equivalents Earned		278	$	50.96
Restricted Stock Units Settled		—	$	—
Restricted Stock Units as of March 31, 2024		33,653	$	42.80

There were 44,125 Restricted Stock Units outstanding as of March 31, 2023 with a weighted average stock price of $40.27. Included in Other Noncurrent Liabilities on the Company’s Consolidated Balance Sheets as of March 31, 2024, March 31, 2023 and December 31, 2023 is $0.8 million, $1.1 million and $0.8 million, respectively, representing the fair value of liabilities associated with the portion of fully vested RSUs that will be settled in cash.

Preferred Stock

There were $0.2 million, or 1,727 shares, of Unitil Energy’s 6.00% Series Preferred Stock outstanding as of March 31, 2024 and December 31, 2023. There were $0.2 million, or 1,861 shares, of Unitil Energy’s 6.00% Series Preferred Stock outstanding as of March 31, 2023. There were less than $0.1 million of total dividends declared on Preferred Stock in each of the three month periods ended March 31, 2024 and March 31, 2023, respectively.

- Definition

The entire disclosure for equity.

+ References

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+ Details

Components of Energy Supply Obligations (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Contractual Obligation [Line Items]
Energy Supply Obligations-Current	$ 7.0	$ 15.0	$ 10.6
Exchange Gas Obligation
Contractual Obligation [Line Items]
Energy Supply Obligations-Current	1.9	6.4	4.0
Renewable Energy Portfolio Standards
Contractual Obligation [Line Items]
Energy Supply Obligations-Current	$ 5.1	$ 8.6	$ 6.6

Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2024

Components of Gas and Electric Operating Revenue

In the following tables, revenue is classified by the types of goods/services rendered and market/customer type.


	Three Months Ended March 31, 2024
Electric and Gas Operating Revenues (millions):	Electric		Gas		Total
Billed and Unbilled Revenue:
Residential	$	40.5	$	41.1	$	81.6
Commercial and Industrial		28.1		55.2		83.3
Other		2.4		4.1		6.5
Total Billed and Unbilled Revenue		71.0		100.4		171.4
Rate Adjustment Mechanism Revenue		2.6		4.7		7.3
Total Electric and Gas Operating Revenues	$	73.6	$	105.1	$	178.7


	Three Months Ended March 31, 2023
Electric and Gas Operating Revenues (millions):	Electric		Gas			Total
Billed and Unbilled Revenue:
Residential	$	60.1	$	49.1		$	109.2
Commercial and Industrial		34.8		69.2			104.0
Other		2.7		3.6			6.3
Total Billed and Unbilled Revenue		97.6		121.9			219.5
Rate Adjustment Mechanism Revenue		10.6		(9.9	)		0.7
Total Electric and Gas Operating Revenues	$	108.2	$	112.0		$	220.2

Allowance for Doubtful Accounts Included in Accounts Receivable Net

The Allowance for Doubtful Accounts as of March 31, 2024, March 31, 2023 and December 31, 2023, was as follows:


	March 31,				December 31,
(millions)	2024		2023		2023
Allowance for Doubtful Accounts	$	2.8	$	3.1	$	2.4

Components of Accrued Revenue

The following table shows the components of Accrued Revenue as of March 31, 2024, March 31, 2023 and December 31, 2023.


	March 31,				December 31,
Accrued Revenue (millions)	2024		2023		2023
Regulatory Assets – Current	$	65.1	$	66.4	$	56.5
Unbilled Revenues, net		7.1		5.2		6.9
Total Accrued Revenue	$	72.2	$	71.6	$	63.4

Components of Exchange Gas Receivable

The following table shows the components of Exchange Gas Receivable as of March 31, 2024, March 31, 2023 and December 31, 2023.


	March 31,				December 31,
Exchange Gas Receivable (millions)	2024		2023		2023
Northern Utilities	$	1.9	$	4.0	$	8.6
Fitchburg		0.3		0.7		0.8
Total Exchange Gas Receivable	$	2.2	$	4.7	$	9.4

Components of Gas Inventory

The following table shows the components of Gas Inventory as of March 31, 2024, March 31, 2023 and December 31, 2023.


	March 31,				December 31,
Gas Inventory (millions)	2024		2023		2023
Natural Gas	$	—	$	0.4	$	0.3
Propane		0.2		0.3		0.3
Liquefied Natural Gas & Other		0.1		0.1		0.4
Total Gas Inventory	$	0.3	$	0.8	$	1.0

Regulatory Assets

The Company currently receives recovery in rates or expects to receive recovery of these hardship accounts in future rate cases.


	March 31,				December 31,
Regulatory Assets consist of the following (millions)	2024		2023		2023
Retirement Benefits	$	27.4	$	28.0	$	29.8
Energy Supply and Other Rate Adjustment Mechanisms		62.3		63.3		52.4
Deferred Storm Charges		7.8		7.7		9.2
Environmental		6.2		6.2		6.1
Income Taxes		0.9		1.6		1.1
Other Deferred Charges		12.6		11.2		11.0
Total Regulatory Assets		117.2		118.0		109.6
Less: Current Portion of Regulatory Assets(1)		65.1		66.4		56.5
Regulatory Assets – noncurrent	$	52.1	$	51.6	$	53.1

Reflects amounts included in the Accrued Revenue on the Company’s Consolidated Balance Sheets.

Regulatory Liabilities


	March 31,				December 31,
Regulatory Liabilities consist of the following (millions)	2024		2023		2023
Income Taxes (Note 8)	$	37.9	$	40.3	$	38.6
Rate Adjustment Mechanisms & Other		14.0		12.9		9.3
Total Regulatory Liabilities		51.9		53.2		47.9
Less: Current Portion of Regulatory Liabilities		17.9		17.0		13.5
Regulatory Liabilities – noncurrent	$	34.0	$	36.2	$	34.4

Fair Value of Marketable Securities

Changes in the fair value of these investments are recorded in Other Expense, Net.


	March 31,				December 31,
Fair Value of Marketable Securities (millions)	2024		2023		2023
Money Market Funds	$	2.0	$	5.7	$	2.0
Fixed Income Funds		3.9		—		4.0
Total Marketable Securities	$	5.9	$	5.7	$	6.0

Components of Energy Supply Obligations

The following discussion and table summarize the nature and amounts of the items recorded as Energy Supply Obligations (current portion) and Other Noncurrent Liabilities (noncurrent portion) on the Company’s Consolidated Balance Sheets.


	March 31,				December 31,
Energy Supply Obligations (millions)	2024		2023		2023
Current:
Exchange Gas Obligation	$	1.9	$	4.0	$	6.4
Renewable Energy Portfolio Standards		5.1		6.6		8.6
Total Energy Supply Obligations	$	7.0	$	10.6	$	15.0

Deferred Compensation Plan [Member]

Fair Value of Marketable Securities

Changes in the fair value of these investments are recorded in Other Expense, Net.


	March 31,				December 31,
Fair Value of Marketable Securities (millions)	2024		2023		2023
Equity Funds	$	1.6	$	0.8	$	1.1
Fixed Income Funds		0.1		—		0.1
Money Market Funds		0.1		0.1		0.1
Total Marketable Securities	$	1.8	$	0.9	$	1.3

Components of Gas and Electric Operating Revenue (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	$ 178.7	$ 220.2
Billed and Unbilled Revenue
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	171.4	219.5
Rate Adjustment Mechanism Revenue
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	7.3	0.7
Electric
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	73.6	108.2
Electric \| Billed and Unbilled Revenue
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	71.0	97.6
Electric \| Rate Adjustment Mechanism Revenue
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	2.6	10.6
Gas Segment
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	105.1	112.0
Gas Segment \| Billed and Unbilled Revenue
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	100.4	121.9
Gas Segment \| Rate Adjustment Mechanism Revenue
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	4.7	(9.9)
Residential
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	81.6	109.2
Residential \| Electric
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	40.5	60.1
Residential \| Gas Segment
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	41.1	49.1
Commercial & Industrial
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	83.3	104.0
Commercial & Industrial \| Electric
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	28.1	34.8
Commercial & Industrial \| Gas Segment
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	55.2	69.2
Other
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	6.5	6.3
Other \| Electric
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	2.4	2.7
Other \| Gas Segment
Operating Revenues [Line Items]
Total Electric and Gas Operating Revenues	$ 4.1	$ 3.6

- Definition

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 924
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-Name Accounting Standards Codification
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+ Details

DEBT AND FINANCING ARRANGEMENTS - Details On Long Term Debt (Parenthetical) (Detail)	3 Months Ended
	Mar. 31, 2024
3.70% Senior Notes, Due August 1, 2026
Debt Instrument [Line Items]
Stated interest rate	3.70%
Debt instrument due date	Aug. 01, 2026
3.43% Senior Notes, Due December 18, 2029
Debt Instrument [Line Items]
Stated interest rate	3.43%
Debt instrument due date	Dec. 18, 2029
First Mortgage Bonds 6.96% Senior Secured Notes, Due September 1, 2028 \| Unitil Energy Systems Inc [Member]
Debt Instrument [Line Items]
Stated interest rate	6.96%
Debt instrument due date	Sep. 01, 2028
First Mortgage Bonds 8.00% Senior Secured Notes, Due May 1, 2031 \| Unitil Energy Systems Inc [Member]
Debt Instrument [Line Items]
Stated interest rate	8.00%
Debt instrument due date	May 01, 2031
First Mortgage Bonds 6.32% Senior Secured Notes, Due September 15, 2036 \| Unitil Energy Systems Inc [Member]
Debt Instrument [Line Items]
Stated interest rate	6.32%
Debt instrument due date	Sep. 15, 2036
3.58% Senior Secured Notes, Due September 15, 2040 \| Unitil Energy Systems Inc [Member]
Debt Instrument [Line Items]
Stated interest rate	3.58%
Debt instrument due date	Sep. 15, 2040
First Mortgage Bonds 4.18% Senior Secured Notes Due November 30, 2048 \| Unitil Energy Systems Inc [Member]
Debt Instrument [Line Items]
Stated interest rate	4.18%
Debt instrument due date	Nov. 30, 2048
6.79% Senior Notes, Due October 15, 2025 \| Fitchburg Gas And Electric Light Company [Member]
Debt Instrument [Line Items]
Stated interest rate	6.79%
Debt instrument due date	Oct. 15, 2025
3.52% Senior Notes, Due November 1, 2027 \| Fitchburg Gas And Electric Light Company [Member]
Debt Instrument [Line Items]
Stated interest rate	3.52%
Debt instrument due date	Nov. 01, 2027
3.52% Senior Notes, Due November 1, 2027 \| Northern Utilities Inc [Member]
Debt Instrument [Line Items]
Stated interest rate	3.52%
Debt instrument due date	Nov. 01, 2027
7.37% Notes, Due January 15, 2029 \| Fitchburg Gas And Electric Light Company [Member]
Debt Instrument [Line Items]
Stated interest rate	7.37%
Debt instrument due date	Jan. 15, 2029
5.90% Notes, Due December 15, 2030 \| Fitchburg Gas And Electric Light Company [Member]
Debt Instrument [Line Items]
Stated interest rate	5.90%
Debt instrument due date	Dec. 15, 2030
7.98% Notes, Due June 1, 2031 \| Fitchburg Gas And Electric Light Company [Member]
Debt Instrument [Line Items]
Stated interest rate	7.98%
Debt instrument due date	Jun. 01, 2031
5.70% Notes, Due July 2, 2033 \| Fitchburg Gas And Electric Light Company [Member]
Debt Instrument [Line Items]
Stated interest rate	5.70%
Debt instrument due date	Jul. 02, 2033
3.78% Senior Notes, Due September 15, 2040 \| Fitchburg Gas And Electric Light Company [Member]
Debt Instrument [Line Items]
Stated interest rate	3.78%
Debt instrument due date	Sep. 15, 2040
3.78% Senior Notes, Due September 15, 2040 \| Northern Utilities Inc [Member]
Debt Instrument [Line Items]
Stated interest rate	3.78%
Debt instrument due date	Sep. 15, 2040
4.32% Senior Notes, Due November 1, 2047 \| Fitchburg Gas And Electric Light Company [Member]
Debt Instrument [Line Items]
Stated interest rate	4.32%
Debt instrument due date	Nov. 01, 2047
4.32% Senior Notes, Due November 1, 2047 \| Northern Utilities Inc [Member]
Debt Instrument [Line Items]
Stated interest rate	4.32%
Debt instrument due date	Nov. 01, 2047
5.96% Senior Notes, Due July 2, 2053 \| Fitchburg Gas And Electric Light Company [Member]
Debt Instrument [Line Items]
Stated interest rate	5.96%
Debt instrument due date	Jul. 02, 2053
7.72% Senior Notes, Due December 3, 2038 \| Northern Utilities Inc [Member]
Debt Instrument [Line Items]
Stated interest rate	7.72%
Debt instrument due date	Dec. 03, 2038
4.42% Senior Notes, Due October 15, 2044 \| Northern Utilities Inc [Member]
Debt Instrument [Line Items]
Stated interest rate	4.42%
Debt instrument due date	Oct. 15, 2044
4.04% Senior Notes, Due September 12, 2049 \| Northern Utilities Inc [Member]
Debt Instrument [Line Items]
Stated interest rate	4.04%
Debt instrument due date	Sep. 12, 2049
3.72% Senior Notes, Due November 1, 2027 \| Granite State Gas Transmission Inc [Member]
Debt Instrument [Line Items]
Stated interest rate	3.72%
Debt instrument due date	Nov. 01, 2027
2.64% Senior Secured Notes, Due December 18, 2030 \| Unitil Realty Corp [Member]
Debt Instrument [Line Items]
Stated interest rate	2.64%
Debt instrument due date	Dec. 18, 2030

CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Current Assets:
Cash and Cash Equivalents	$ 6.3	$ 6.5	$ 6.8
Accounts Receivable, Net	83.9	75.0	92.2
Accrued Revenue	72.2	63.4	71.6
Exchange Gas Receivable	2.2	9.4	4.7
Gas Inventory	0.3	1.0	0.8
Materials and Supplies	14.0	13.5	12.4
Prepayments and Other	10.5	8.3	9.4
Total Current Assets	189.4	177.1	197.9
Utility Plant:
Electric	659.8	654.9	629.9
Gas	1,129.6	1,117.6	1,055.0
Common	64.9	70.0	68.9
Construction Work in Progress	68.5	65.3	53.8
Utility Plant	1,922.8	1,907.8	1,807.6
Less: Accumulated Depreciation	493.0	486.9	466.3
Net Utility Plant	1,429.8	1,420.9	1,341.3
Other Noncurrent Assets:
Regulatory Assets	52.1	53.1	51.6
Operating Lease Right of Use Assets	5.6	5.6	5.7
Other Assets	21.0	13.7	18.2
Total Other Noncurrent Assets	78.7	72.4	75.5
TOTAL ASSETS	1,697.9	1,670.4	1,614.7
Current Liabilities:
Accounts Payable	37.9	47.7	46.3
Short-Term Debt	169.9	162.0	140.2
Long-Term Debt, Current Portion	4.9	4.9	6.7
Regulatory Liabilities	17.9	13.5	17.0
Energy Supply Obligations	7.0	15.0	10.6
Interest Payable	7.2	6.0	6.1
Environmental Obligations	0.7	0.6	0.6
Taxes Payable	8.9	1.9	1.2
Other Current Liabilities	22.2	25.7	24.8
Total Current Liabilities	276.6	277.3	253.5
Noncurrent Liabilities:
Retirement Benefit Obligations	46.0	45.6	46.8
Deferred Income Taxes, Net	179.1	176.1	171.1
Cost of Removal Obligations	130.6	126.3	120.0
Regulatory Liabilities	34.0	34.4	36.2
Environmental Obligations	4.1	4.0	4.1
Other Noncurrent Liabilities	8.8	8.3	8.6
Total Noncurrent Liabilities	402.6	394.7	386.8
Capitalization:
Long-Term Debt, Less Current Portion	507.9	509.1	488.0
Stockholders' Equity:
Common Equity (Authorized: 25,000,000 and Outstanding: 16,167,887, 16,086,230 and 16,116,724 Shares)	338.7	337.6	336.1
Retained Earnings	171.9	151.5	150.1
Total Common Stock Equity	510.6	489.1	486.2
Preferred Stock	0.2	0.2	0.2
Total Stockholders' Equity	510.8	489.3	486.4
Total Capitalization	1,018.7	998.4	974.4
Commitments and Contingencies (Notes 6 & 7)
TOTAL LIABILITIES AND CAPITALIZATION	$ 1,697.9	$ 1,670.4	$ 1,614.7

Environmental Matters (Tables)

3 Months Ended

Mar. 31, 2024

Text Block [Abstract]

Environmental Obligations Recognized by Company

The following table sets forth a summary of changes in the Company’s liability for Environmental Obligations for the three months ended March 31, 2024 and 2023.


Environmental Obligations (millions)
	March 31,
	2024		2023
Total Balance at Beginning of Period	$	4.6	$	4.4
Additions		0.3		0.5
Less: Payments / Reductions		0.1		0.2
Total Balance at End of Period		4.8		4.7
Less: Current Portion		0.7		0.6
Noncurrent Balance at End of Period	$	4.1	$	4.1

Segment Information

3 Months Ended

Mar. 31, 2024

Segment Information

note 3 - Segment Information

The following table provides significant segment financial data for the three months ended March 31, 2024 and March 31, 2023.


	Electric		Gas			Other			Total
Three Months Ended March 31, 2024 (millions)
Revenues:
Billed and Unbilled Revenue	$	71.0	$	100.4		$	—		$	171.4
Rate Adjustment Mechanism Revenue		2.6		4.7			—			7.3
Total Operating Revenues		73.6		105.1			—			178.7
Segment Profit (Loss)		4.9		22.4			(0.1	)		27.2
Capital Expenditures		8.7		10.7			0.8			20.2
Segment Assets		625.5		1,043.7			28.7			1,697.9

Three Months Ended March 31, 2023 (millions)
Revenues:
Billed and Unbilled Revenue	$	97.6	$	121.9		$	—		$	219.5
Rate Adjustment Mechanism Revenue		10.6		(9.9	)		—			0.7
Total Operating Revenues		108.2		112.0			—			220.2
Segment Profit (Loss)		5.3		19.0			(0.2	)		24.1
Capital Expenditures		10.6		11.5			0.1			22.2
Segment Assets		613.7		979.2			21.8			1,614.7

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-15

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-42

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-40

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//280/tableOfContent

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-26

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-34

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-41

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-21

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-21

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

+ Details

Segment Information (Tables)

3 Months Ended

Mar. 31, 2024

Significant Segment Financial Data

he following table provides significant segment financial data for the three months ended March 31, 2024 and March 31, 2023.


	Electric		Gas			Other			Total
Three Months Ended March 31, 2024 (millions)
Revenues:
Billed and Unbilled Revenue	$	71.0	$	100.4		$	—		$	171.4
Rate Adjustment Mechanism Revenue		2.6		4.7			—			7.3
Total Operating Revenues		73.6		105.1			—			178.7
Segment Profit (Loss)		4.9		22.4			(0.1	)		27.2
Capital Expenditures		8.7		10.7			0.8			20.2
Segment Assets		625.5		1,043.7			28.7			1,697.9

Three Months Ended March 31, 2023 (millions)
Revenues:
Billed and Unbilled Revenue	$	97.6	$	121.9		$	—		$	219.5
Rate Adjustment Mechanism Revenue		10.6		(9.9	)		—			0.7
Total Operating Revenues		108.2		112.0			—			220.2
Segment Profit (Loss)		5.3		19.0			(0.2	)		24.1
Capital Expenditures		10.6		11.5			0.1			22.2
Segment Assets		613.7		979.2			21.8			1,614.7

Components of Accrued Revenue (Detail) - USD ($)
$ in Millions

Mar. 31, 2024

Dec. 31, 2023

Mar. 31, 2023

Deferred Revenue Arrangement [Line Items]

Regulatory Assets, Current

^[1]

$ 65.1

$ 56.5

$ 66.4

Total Accrued Revenue

72.2

63.4

71.6

Unbilled Revenues

Deferred Revenue Arrangement [Line Items]

Regulatory Assets, Current

7.1

6.9

5.2

Regulatory Assets

Deferred Revenue Arrangement [Line Items]

Regulatory Assets, Current

$ 65.1

$ 56.5

$ 66.4

[1]	Reflects amounts included in the Accrued Revenue on the Company’s Consolidated Balance Sheets.

Retirement Benefit Obligations - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, assumed health care cost trend rate, description	The health care cost trend rate used to determine benefit plan costs for 2024 for pre-65 retirees is 8.00%, with an ultimate rate of 4.50% in 2033, and for post-65 retirees, the health care cost trend rate is 6.00%, with an ultimate rate of 4.50% in 2033. The health care cost trend rate used to determine benefit plan costs for 2023 for pre-65 retirees was 8.00%, with an ultimate rate of 4.50% in 2030, and for post-65 retirees, the health care cost trend rate was 6.25%, with an ultimate rate of 4.50% in 2030.
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 0.0
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	0.0
Supplemental Employee Retirement Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Benefit payments under SERP Plan	0.2
Expected additional benefit payments for the remainder of 2020	$ 0.5
Pre-65 retirees
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate, assumed	8.00%	8.00%
Health care cost trend rate, ultimate rate	4.50%	4.50%
Health care cost trend rate, ultimate rate in year	2033	2030
Post-65 retirees
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate, assumed	6.00%	6.25%
Health care cost trend rate, ultimate rate	4.50%	4.50%
Health care cost trend rate, ultimate rate in year	2033	2030

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 1 - Summary of Significant Accounting Policies

Nature of Operations - Unitil Corporation (Unitil or the Company) is a public utility holding company. Unitil and its subsidiaries are subject to regulation as a holding company system by the Federal Energy Regulatory Commission (FERC) under the Energy Policy Act of 2005. The following companies are wholly-owned subsidiaries of Unitil: Unitil Energy Systems, Inc. (Unitil Energy), Fitchburg Gas and Electric Light Company (Fitchburg), Northern Utilities, Inc. (Northern Utilities), Granite State Gas Transmission, Inc. (Granite State), Unitil Power Corp. (Unitil Power), Unitil Realty Corp. (Unitil Realty), Unitil Service Corp. (Unitil Service) and its non-regulated business unit Unitil Resources, Inc. (Unitil Resources).

The Company’s earnings historically have been seasonal and typically higher in the first and fourth quarters when customers use gas for heating purposes.

Unitil’s principal business is the local distribution of electricity in the southeastern seacoast and capital city areas of New Hampshire and the greater Fitchburg area of north central Massachusetts and the local distribution of gas in southeastern New Hampshire, portions of southern Maine to the Lewiston-Auburn area and in the greater Fitchburg area of north central Massachusetts. Unitil has three distribution utility subsidiaries, including Unitil Energy, which operates in New Hampshire; Fitchburg, which operates in Massachusetts; and Northern Utilities, which operates in New Hampshire and Maine (collectively referred to as the “distribution utilities”).

Granite State is an interstate gas transmission pipeline company, operating 85 miles of underground gas transmission pipeline primarily located in Maine and New Hampshire. Granite State provides Northern Utilities with interconnection to three major gas pipelines and access to domestic gas supplies in the south and Canadian gas supplies in the north. Granite State derives its revenues principally from transportation services provided to Northern Utilities and, to a lesser extent, third-party marketers.

A fifth utility subsidiary, Unitil Power, formerly functioned as the full requirements wholesale power supply provider for Unitil Energy, but ceased being the wholesale supplier of Unitil Energy with the implementation of industry restructuring and divested its long-term power supply contracts.

Unitil also has three other wholly-owned subsidiaries: Unitil Service, Unitil Resources and Unitil Realty. Unitil Service provides, at cost, a variety of administrative and professional services, including regulatory, financial, accounting, human resources, engineering, operations, technology, energy management and management services on a centralized basis to its affiliated Unitil companies. Unitil Resources is the Company’s wholly-owned non-regulated subsidiary, which currently does not have any activity. Unitil Realty owns and manages the Company’s corporate office in Hampton, New Hampshire and leases this facility to Unitil Service under a long-term lease arrangement. Unitil Realty also owns land for future use in Kingston, New Hampshire.

Basis of Presentation - The accompanying unaudited consolidated financial statements of Unitil have been prepared in accordance with the instructions to Form 10-Q and include the information and footnotes required by generally accepted accounting principles. In the opinion of management, all adjustments considered necessary for a fair presentation have been included. The results of operations for the three months ended March 31, 2024 are not necessarily indicative of results to be expected for the year ending December 31, 2024. For additional information, refer to Note 1 of Part II to the Consolidated Financial Statements – “Summary of Significant Accounting Policies” of the Company’s Form 10-K for the year ended December 31, 2023, as filed with the Securities and Exchange Commission (SEC) on February 13, 2024, for a description of the Company’s Basis of Presentation.

Utility Revenue Recognition - Electric Operating Revenues and Gas Operating Revenues consist of billed and unbilled revenue and revenue from rate adjustment mechanisms. Billed and unbilled revenue includes delivery revenue and pass-through revenue, recognized according to tariffs approved by federal and state regulatory commissions, which determine the amount of revenue the Company will record for these items. Revenue from rate adjustment mechanisms is accrued revenue, recognized in connection with rate adjustment mechanisms, and authorized by regulators for recognition in the current period for future cash recoveries from, or credits to, customers.

Revenue is recorded when service is rendered or energy is delivered to customers. However, the determination of energy sales to individual customers is based on the reading of their meters, which occurs on a systematic basis throughout the month. At the end of each calendar month, amounts of energy delivered to customers since the date of the last meter reading are estimated and the corresponding unbilled revenues are calculated. These unbilled revenues are estimated each month based on estimated customer usage by class and applicable customer rates, taking into account current and historical weather data, assumptions pertaining to metering patterns, billing cycle statistics, and other estimates and assumptions, and are then reversed in the following month when billed to customers.

A majority of the Company’s revenue from contracts with customers continues to be recognized on a monthly basis based on applicable tariffs and customer monthly consumption. Such revenue is recognized using the invoice practical expedient, which allows an entity to recognize revenue in the amount that directly corresponds to the value transferred to the customer.

The Company’s billed and unbilled revenue meets the definition of “revenues from contracts with customers” as defined in Accounting Standards Codification (ASC) 606. Revenue recognized in connection with rate adjustment mechanisms is consistent with the definition of alternative revenue programs in ASC 980-605-25-3, as the Company has the ability to adjust rates in the future as a result of past activities or completed events. The rate adjustment mechanisms meet the criteria within ASC 980-605-25-4. In cases where allowable costs are greater than operating revenues billed in the current period for the individual rate adjustment mechanism, additional operating revenue is recognized. In cases where allowable costs are less than operating revenues billed in the current period for the individual rate adjustment mechanism, operating revenue is reduced. ASC 606 requires the Company to disclose separately the amount of revenues from contracts with customers and alternative revenue program revenues.

In the following tables, revenue is classified by the types of goods/services rendered and market/customer type.


	Three Months Ended March 31, 2024
Electric and Gas Operating Revenues (millions):	Electric		Gas		Total
Billed and Unbilled Revenue:
Residential	$	40.5	$	41.1	$	81.6
Commercial and Industrial		28.1		55.2		83.3
Other		2.4		4.1		6.5
Total Billed and Unbilled Revenue		71.0		100.4		171.4
Rate Adjustment Mechanism Revenue		2.6		4.7		7.3
Total Electric and Gas Operating Revenues	$	73.6	$	105.1	$	178.7


	Three Months Ended March 31, 2023
Electric and Gas Operating Revenues (millions):	Electric		Gas			Total
Billed and Unbilled Revenue:
Residential	$	60.1	$	49.1		$	109.2
Commercial and Industrial		34.8		69.2			104.0
Other		2.7		3.6			6.3
Total Billed and Unbilled Revenue		97.6		121.9			219.5
Rate Adjustment Mechanism Revenue		10.6		(9.9	)		0.7
Total Electric and Gas Operating Revenues	$	108.2	$	112.0		$	220.2

Revenue decoupling is the term given to the elimination of the dependency of a utility’s distribution revenue on the volume of electricity or gas sales. The difference between distribution revenue amounts billed to customers and the targeted revenue decoupling amounts is recognized as an increase or a decrease in Accrued Revenue, which forms the basis for resetting rates for future cash recoveries from, or credits to, customers. These revenue decoupling targets may be adjusted as a result of rate cases and other authorized adjustments that the Company files with the Massachusetts Department of Public Utilities (MDPU) and New Hampshire Public Utilities Commission (NHPUC). Fitchburg has been subject to revenue decoupling since 2011. Unitil Energy has been subject to revenue decoupling since June 1, 2022. As a result of Unitil Energy now being subject to revenue decoupling, as of June 1, 2022, revenue decoupling now applies to substantially all of Unitil’s total annual electric sales volumes. Substantially all of Northern Utilities’ gas sales volumes in New Hampshire have been subject to decoupling since August 1, 2022. The Company's electric and gas sales in New Hampshire and Massachusetts are now largely decoupled.

Income Taxes - The Company is subject to Federal and State income taxes and various other business taxes. The Company’s process for determining income tax amounts involves estimating the Company’s current tax liabilities, and assessing temporary and permanent differences resulting from the timing of the deductions of expenses and recognition of taxable income for tax and book accounting purposes. These temporary differences result in deferred tax assets and liabilities, which are included in the Company’s Consolidated

Balance Sheets. The Company accounts for income tax assets, liabilities and expenses in accordance with the Financial Accounting Standards Board (FASB) Codification guidance on Income Taxes. The Company classifies penalties and interest expense related to income tax liabilities as income tax expense and interest expense, respectively, in the Consolidated Statements of Earnings.

Provisions for income taxes are calculated in each jurisdiction in which the Company operates, for each period for which a statement of earnings is presented. The Company accounts for income taxes in accordance with the FASB Codification guidance on Income Taxes, which requires an asset and liability approach for the financial accounting and reporting of income taxes. Significant judgments and estimates are required in determining the current and deferred tax assets and liabilities. The Company’s deferred tax assets and liabilities reflect its best assessment of estimated future taxes to be paid. In accordance with the FASB Codification, the Company periodically assesses the realization of its deferred tax assets and liabilities and adjusts the income tax provision, the current tax liability and deferred taxes in the period in which the facts and circumstances which gave rise to the revision become known.

Cash and Cash Equivalents - Cash and Cash Equivalents includes all cash and cash equivalents to which the Company has legal title. Cash equivalents include short-term investments with original maturities of three months or less and interest bearing deposits. The Company’s cash and cash equivalents are held at financial institutions and at times may exceed federally insured limits. The Company has not experienced any losses in such accounts. Under the Independent System Operator—New England (ISO-NE) Financial Assurance Policy (Policy), Unitil’s subsidiaries Unitil Energy, Fitchburg and Unitil Power are required to provide assurance of their ability to satisfy their obligations to ISO-NE. Under this Policy, Unitil’s subsidiaries provide cash deposits covering approximately 2-1/2 months of outstanding obligations, less credit amounts that are based on the Company’s credit rating. As of March 31, 2024, March 31, 2023 and December 31, 2023, the Unitil subsidiaries had deposited $3.1 million, $4.2 million and $3.3 million, respectively to satisfy their ISO-NE obligations.

Allowance for Doubtful Accounts - The Company recognizes a provision for doubtful accounts that reflects the Company’s estimate of expected credit losses for electric and gas utility service accounts receivable. The allowance for doubtful accounts is calculated by applying a historical loss rate to customer account balances, and reflects management’s assessment of current and expected economic conditions, customer trends, or other factors such as the extent and duration of any shutoff or collection moratoriums. The Company also calculates the amount of written-off receivables that are recoverable through regulatory rate reconciling mechanisms. The Company’s distribution utilities are authorized by regulators to recover the costs of the energy commodity portion of bad debts through rate mechanisms. Also, the electric and gas divisions of Fitchburg are authorized to recover through rates past due amounts associated with protected hardship accounts. Evaluating the adequacy of the allowance for doubtful accounts requires judgment about the assumptions used in the analysis. The Company’s experience has been that the assumptions used in evaluating the adequacy of the allowance for doubtful accounts have proven to be reasonably accurate.

The Allowance for Doubtful Accounts as of March 31, 2024, March 31, 2023 and December 31, 2023, was as follows:


	March 31,				December 31,
(millions)	2024		2023		2023
Allowance for Doubtful Accounts	$	2.8	$	3.1	$	2.4

Accounts Receivable, Net includes $2.7 million, $3.0 million, and $2.3 million of the Allowance for Doubtful Accounts at March 31, 2024, March 31, 2023 and December 31, 2023, respectively. Unbilled Revenues, net (a component of Accrued Revenue) includes $0.1 million, $0.1 million and $0.1 million of the Allowance for Doubtful Accounts at March 31, 2024, March 31, 2023 and December 31, 2023, respectively.

Accrued Revenue - Accrued Revenue includes the current portion of Regulatory Assets and unbilled revenues. The following table shows the components of Accrued Revenue as of March 31, 2024, March 31, 2023 and December 31, 2023.


	March 31,				December 31,
Accrued Revenue (millions)	2024		2023		2023
Regulatory Assets – Current	$	65.1	$	66.4	$	56.5
Unbilled Revenues, net		7.1		5.2		6.9
Total Accrued Revenue	$	72.2	$	71.6	$	63.4

Exchange Gas Receivable - Northern Utilities and Fitchburg have gas exchange and storage agreements whereby gas purchases during the months of April through October are delivered to a third party. The third party delivers gas back to the Company during the months of November through March. The exchange and storage gas volumes are recorded at weighted average cost. The following table shows the components of Exchange Gas Receivable as of March 31, 2024, March 31, 2023 and December 31, 2023.


	March 31,				December 31,
Exchange Gas Receivable (millions)	2024		2023		2023
Northern Utilities	$	1.9	$	4.0	$	8.6
Fitchburg		0.3		0.7		0.8
Total Exchange Gas Receivable	$	2.2	$	4.7	$	9.4

Gas Inventory - The Company uses the weighted average cost methodology to value gas inventory. The following table shows the components of Gas Inventory as of March 31, 2024, March 31, 2023 and December 31, 2023.


	March 31,				December 31,
Gas Inventory (millions)	2024		2023		2023
Natural Gas	$	—	$	0.4	$	0.3
Propane		0.2		0.3		0.3
Liquefied Natural Gas & Other		0.1		0.1		0.4
Total Gas Inventory	$	0.3	$	0.8	$	1.0

Utility Plant - The cost of additions to Utility Plant and the cost of renewals and betterments are capitalized. Cost consists of labor, materials, services and certain indirect construction costs, including an allowance for funds used during construction (AFUDC). The costs of current repairs and minor replacements are charged to appropriate operating expense accounts. The original cost of utility plant retired or otherwise disposed of is charged to the accumulated provision for depreciation. The Company includes in its mass asset depreciation rates, which are periodically reviewed as part of its ratemaking proceedings, cost of removal amounts to provide for future negative salvage value. At March 31, 2024, March 31, 2023 and December 31, 2023, the cost of removal amounts, which are recorded on the Consolidated Balance Sheets in Cost of Removal Obligations, were estimated to be $130.6 million, $120.0 million, and $126.3 million, respectively.

Leases - The Company records assets and liabilities on the balance sheet for all leases with terms longer than 12 months. Leases are classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. The Company has elected the practical expedient to not separate non-lease components from lease components and instead to account for both as a single lease component. The Company’s accounting policy election for leases with a lease term of 12 months or less is to recognize the lease payments as lease expense in the Consolidated Statements of Earnings on a straight-line basis over the lease term. See additional discussion in the “Leases” section of Note 4 (Debt and Financing Arrangements).

Regulatory Accounting - The Company’s principal business is the distribution of electricity and natural gas by the three distribution utilities: Unitil Energy, Fitchburg and Northern Utilities. Unitil Energy and Fitchburg are subject to regulation by the FERC. Fitchburg is also regulated by the MDPU, Unitil Energy is regulated by the NHPUC and Northern Utilities is regulated by the MPUC and NHPUC. Granite State, the Company’s natural gas transmission pipeline, is regulated by the FERC. Accordingly, the Company uses the Regulated Operations guidance as set forth in the FASB Codification. The Company has recorded Regulatory Assets and Regulatory Liabilities which will be recovered from customers, or applied for customer benefit, in accordance with rate provisions approved by the applicable public utility regulatory commission. The electric and gas divisions of Fitchburg are authorized to recover through rates past due amounts associated with hardship accounts that are protected from shut-off. As of March 31, 2024, March 31, 2023 and December 31, 2023, the Company has recorded $6.9 million, $5.8 million and $6.0 million, respectively, of hardship accounts in Regulatory Assets. These amounts are included in “Other Deferred Charges” in the following table. The Company currently receives recovery in rates or expects to receive recovery of these hardship accounts in future rate cases.


	March 31,				December 31,
Regulatory Assets consist of the following (millions)	2024		2023		2023
Retirement Benefits	$	27.4	$	28.0	$	29.8
Energy Supply and Other Rate Adjustment Mechanisms		62.3		63.3		52.4
Deferred Storm Charges		7.8		7.7		9.2
Environmental		6.2		6.2		6.1
Income Taxes		0.9		1.6		1.1
Other Deferred Charges		12.6		11.2		11.0
Total Regulatory Assets		117.2		118.0		109.6
Less: Current Portion of Regulatory Assets(1)		65.1		66.4		56.5
Regulatory Assets – noncurrent	$	52.1	$	51.6	$	53.1

(1)

Reflects amounts included in the Accrued Revenue on the Company’s Consolidated Balance Sheets.


	March 31,				December 31,
Regulatory Liabilities consist of the following (millions)	2024		2023		2023
Income Taxes (Note 8)	$	37.9	$	40.3	$	38.6
Rate Adjustment Mechanisms & Other		14.0		12.9		9.3
Total Regulatory Liabilities		51.9		53.2		47.9
Less: Current Portion of Regulatory Liabilities		17.9		17.0		13.5
Regulatory Liabilities – noncurrent	$	34.0	$	36.2	$	34.4

Generally, the Company receives a return on investment on its regulatory assets for which a cash outflow has been made. Included in Regulatory Assets as of March 31, 2024 are $6.9 million of environmental costs, rate case costs and other expenditures to be recovered over varying periods in the next seven years. Regulators have authorized recovery of these expenditures, but without a return. Regulatory commissions can reach different conclusions about the recovery of costs, which can have a material effect on the Company’s Consolidated Financial Statements. The Company believes it is probable that its regulated distribution and transmission utilities will recover their investments in long-lived assets, including regulatory assets. If the Company, or a portion of its assets or operations, were to cease meeting the criteria for application of these accounting rules, accounting standards for businesses in general would become applicable and immediate recognition of any previously deferred costs, or a portion of deferred costs, would be required in the year in which the criteria are no longer met, if such deferred costs were not recoverable in the portion of the business that continues to meet the criteria for application of the FASB Codification topic on Regulated Operations. If unable to continue to apply the FASB Codification provisions for Regulated Operations, the Company would be required to apply the provisions for the Discontinuation of Rate-Regulated Accounting included in the FASB Codification. In the Company’s opinion, its regulated operations will be subject to the FASB Codification provisions for Regulated Operations for the foreseeable future.

Derivatives - The Company’s regulated energy subsidiaries enter into energy supply contracts to serve their electric and gas customers. The Company has determined that its energy supply contracts either do not qualify as a derivative instrument under the guidance set forth in the FASB Codification, have been elected as a normal purchase, or have contingencies that have not yet been met in order to establish a notional amount.

Fitchburg has entered into power purchase agreements for which contingencies exist (see Note 6, Regulatory Matters—Fitchburg—Massachusetts Request for Proposal (RFPs)). Until these contingencies are satisfied, these contracts will not qualify for derivative accounting. The Company believes that the power purchase obligations under these long-term contracts will have a material effect on the contractual obligations of Fitchburg.

Investments in Marketable Securities - The Company maintains a trust through which it invests in a money market fund. This fund is intended to satisfy obligations under the Company’s Supplemental Executive Retirement Plan (SERP) (See additional discussion of the SERP in Note 9).

At March 31, 2024, March 31, 2023 and December 31, 2023, the fair value of the Company’s investments in these trading securities, which are recorded on the Consolidated Balance Sheets in Other Assets, was $5.9 million, $5.7 million and $6.0 million, respectively, as shown in the following table. These investments are valued based on quoted prices from active markets and are categorized in Level 1 as they are actively traded and no valuation adjustments have been applied. Changes in the fair value of these investments are recorded in Other Expense, Net.


	March 31,				December 31,
Fair Value of Marketable Securities (millions)	2024		2023		2023
Money Market Funds	$	2.0	$	5.7	$	2.0
Fixed Income Funds		3.9		—		4.0
Total Marketable Securities	$	5.9	$	5.7	$	6.0

The Company also sponsors the Unitil Corporation Deferred Compensation Plan (the “DC Plan”). The DC Plan is a non-qualified deferred compensation plan that provides a vehicle for participants to accumulate tax-deferred savings to supplement retirement income. The DC Plan, which was effective January 1, 2019, is open to senior management or other highly compensated employees as determined by the Company’s Board of Directors, and may also be used for recruitment and retention purposes for newly hired senior executives. The DC Plan design mirrors the Company’s Tax Deferred Savings and Investment Plan formula, but provides for contributions on compensation above the IRS limit, which will allow participants to defer up to 85% of base salary, and up to 85% of

any cash incentive for retirement. The Company may also elect to make discretionary contributions on behalf of any participant in an amount determined by the Company’s Board of Directors. A trust has been established to invest the funds associated with the DC Plan.

At March 31, 2024, March 31, 2023 and December 31, 2023, the fair value of the Company’s investments in these trading securities related to the DC Plan, which are recorded on the Consolidated Balance Sheets in Other Assets, were $1.8 million, $0.9 million and $1.3 million, respectively, as shown in the following table. These investments are valued based on quoted prices from active markets and are categorized in Level 1 as they are actively traded and no valuation adjustments have been applied. Changes in the fair value of these investments are recorded in Other Expense, Net.


	March 31,				December 31,
Fair Value of Marketable Securities (millions)	2024		2023		2023
Equity Funds	$	1.6	$	0.8	$	1.1
Fixed Income Funds		0.1		—		0.1
Money Market Funds		0.1		0.1		0.1
Total Marketable Securities	$	1.8	$	0.9	$	1.3

Energy Supply Obligations - The following discussion and table summarize the nature and amounts of the items recorded as Energy Supply Obligations (current portion) and Other Noncurrent Liabilities (noncurrent portion) on the Company’s Consolidated Balance Sheets.


	March 31,				December 31,
Energy Supply Obligations (millions)	2024		2023		2023
Current:
Exchange Gas Obligation	$	1.9	$	4.0	$	6.4
Renewable Energy Portfolio Standards		5.1		6.6		8.6
Total Energy Supply Obligations	$	7.0	$	10.6	$	15.0

Exchange Gas Obligation - Northern Utilities enters into gas exchange agreements under which Northern Utilities releases certain gas pipeline and storage assets, sells the gas storage inventory to an asset manager and subsequently repurchases the inventory over the course of the gas heating season at the same price at which it sold the gas inventory to the asset manager. The gas inventory related to these agreements is recorded in Exchange Gas Receivable on the Company’s Consolidated Balance Sheets while the corresponding obligations are recorded in Energy Supply Obligations.

Renewable Energy Portfolio Standards - Renewable Energy Portfolio Standards (RPS) require retail electricity suppliers, including public utilities, to demonstrate that required percentages of their sales are met with power generated from certain types of resources or technologies. Compliance is demonstrated by purchasing and retiring Renewable Energy Certificates (REC) generated by facilities approved by the state as qualifying for REC treatment. Unitil Energy and Fitchburg purchase RECs in compliance with RPS legislation in New Hampshire and Massachusetts for supply provided to default service customers. RPS compliance costs are a supply cost that is recovered in customer default service rates. Unitil Energy and Fitchburg collect RPS compliance costs from customers throughout the year and demonstrate compliance for each calendar year on the following July 1. Due to timing differences between collection of revenue from customers and payment of REC costs to suppliers, Unitil Energy and Fitchburg typically defer costs for RPS compliance which are recorded within Accrued Revenue with a corresponding liability in Energy Supply Obligations on the Company’s Consolidated Balance Sheets.

Fitchburg has entered into long-term renewable contracts for the purchase of clean energy and/or RECs pursuant to Massachusetts legislation, specifically, An Act Relative to Green Communities (Green Communities Act, 2008), An Act Relative to Competitively Priced Electricity in the Commonwealth (2012) and An Act to Promote Energy Diversity (Energy Diversity Act, 2016). The generating facilities associated with ten of these contracts have been constructed and are now operating. Three approved contracts are currently under development. These include long-term contracts filed with the MDPU in 2018, two for offshore wind generation (totaling 1,200 MW) and one for imported hydroelectric power and associated transmission, all three of which were approved in 2019. Four offshore wind contracts, totaling 2,400 MW, previously solicited for pursuant to the Green Communities Act and approved by the MDPU in 2021 and 2022, were subsequently terminated in August and September 2023. In compliance with the Green Communities Act as amended by the Energy Diversity Act and the Act Driving Clean Energy and Offshore Wind in coordination with the other electric distribution companies (EDCs) in Massachusetts, on August 30, 2023 the Company issued a fourth offshore wind Request for Proposal seeking to procure at least 400 MW and up to the maximum amount remaining of the statutory requirement under Section 83C of 5,600 MW. On January 18, 2024, the EDCs notified the MDPU that they are extending the bid

submission date and subsequent solicitation schedule dates by an additional 56 days each to allow bidders the opportunity to gain more certainty around their eligibility for the investment tax credit and factor it into their proposals. The submission date was moved to March 27, 2024. The EDCs received bids for Offshore Wind Generation from three developers and are currently evaluating the proposals. Fitchburg recovers the costs associated with long-term renewable contracts on a fully reconciling basis through a MDPU-approved cost recovery mechanism, and has received remuneration for entering into them.

Subsequent Events - The Company evaluates all events or transactions through the date of the related filing. During the period through the date of this filing, the Company did not have any material subsequent events that would result in adjustment to or disclosure in its Consolidated Financial Statements.

CONSOLIDATED STATEMENTS OF CHANGES IN COMMON STOCK EQUITY (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Equity [Abstract]
Dividends per Common Share	$ 0.425	$ 0.405
Common stock, shares issued	5,803	5,335

Components of Gas Inventory (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Public Utilities, Inventory [Line Items]
Weighted average cost inventory amount	$ 0.3	$ 1.0	$ 0.8
Liquefied Natural Gas & Other
Public Utilities, Inventory [Line Items]
Weighted average cost inventory amount	0.1	0.4	0.1
Natural Gas
Public Utilities, Inventory [Line Items]
Weighted average cost inventory amount	0.0	0.3	0.4
Propane
Public Utilities, Inventory [Line Items]
Weighted average cost inventory amount	$ 0.2	$ 0.3	$ 0.3

CONSOLIDATED STATEMENTS OF EARNINGS - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating Revenues
Total Operating Revenues	$ 178.7	$ 220.2
Operating Expenses
Operation and Maintenance	18.2	18.1
Depreciation and Amortization	18.0	16.7
Taxes Other Than Income Taxes	7.7	7.3
Total Operating Expenses	134.5	180.7
Operating Income	44.2	39.5
Interest Expense, Net	7.3	7.1
Other Expense (Income), Net	0.3	0.0
Income Before Income Taxes	36.6	32.4
Provision for Income Taxes	9.4	8.3
Net Income Applicable to Common Shares	$ 27.2	$ 24.1
Net Income Per Common Share-Basic	$ 1.69	$ 1.51
Net Income Per Common Share-Diluted	$ 1.69	$ 1.51
Weighted Average Common Shares Outstanding-Basic	16.1	16.0
Weighted Average Common Shares Outstanding-Diluted	16.1	16.0
Electric
Operating Revenues
Total Operating Revenues	$ 73.6	$ 108.2
Operating Expenses
Cost of Sales	46.5	81.5
Gas
Operating Revenues
Total Operating Revenues	105.1	112.0
Operating Expenses
Cost of Sales	$ 44.1	$ 57.1

CONSOLIDATED BALANCE SHEETS (Parenthetical) - shares	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Statement of Financial Position [Abstract]
Common Stock Authorized	25,000,000	25,000,000	25,000,000
Common Equity Outstanding	16,167,887	16,116,724	16,086,230

Environmental Matters - Company's Liability for Environmental Obligations (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Environmental Exit Cost [Line Items]
Total Balance at Beginning of Period	$ 4.6	$ 4.4
Additions	0.3	0.5
Less: Payments / Reductions	0.1	0.2
Total Balance at End of Period	4.8	4.7
Less: Current Portion	0.7	0.6	$ 0.6
Noncurrent Balance at End of Period	$ 4.1	$ 4.1	$ 4.0

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Nature of Operations

The Company’s earnings historically have been seasonal and typically higher in the first and fourth quarters when customers use gas for heating purposes.

Basis of Presentation

Utility Revenue Recognition

In the following tables, revenue is classified by the types of goods/services rendered and market/customer type.


	Three Months Ended March 31, 2024
Electric and Gas Operating Revenues (millions):	Electric		Gas		Total
Billed and Unbilled Revenue:
Residential	$	40.5	$	41.1	$	81.6
Commercial and Industrial		28.1		55.2		83.3
Other		2.4		4.1		6.5
Total Billed and Unbilled Revenue		71.0		100.4		171.4
Rate Adjustment Mechanism Revenue		2.6		4.7		7.3
Total Electric and Gas Operating Revenues	$	73.6	$	105.1	$	178.7


	Three Months Ended March 31, 2023
Electric and Gas Operating Revenues (millions):	Electric		Gas			Total
Billed and Unbilled Revenue:
Residential	$	60.1	$	49.1		$	109.2
Commercial and Industrial		34.8		69.2			104.0
Other		2.7		3.6			6.3
Total Billed and Unbilled Revenue		97.6		121.9			219.5
Rate Adjustment Mechanism Revenue		10.6		(9.9	)		0.7
Total Electric and Gas Operating Revenues	$	108.2	$	112.0		$	220.2

Income Taxes

Cash and Cash Equivalents

Allowance for Doubtful Accounts

The Allowance for Doubtful Accounts as of March 31, 2024, March 31, 2023 and December 31, 2023, was as follows:


	March 31,				December 31,
(millions)	2024		2023		2023
Allowance for Doubtful Accounts	$	2.8	$	3.1	$	2.4

Accrued Revenue


	March 31,				December 31,
Accrued Revenue (millions)	2024		2023		2023
Regulatory Assets – Current	$	65.1	$	66.4	$	56.5
Unbilled Revenues, net		7.1		5.2		6.9
Total Accrued Revenue	$	72.2	$	71.6	$	63.4

Exchange Gas Receivable


	March 31,				December 31,
Exchange Gas Receivable (millions)	2024		2023		2023
Northern Utilities	$	1.9	$	4.0	$	8.6
Fitchburg		0.3		0.7		0.8
Total Exchange Gas Receivable	$	2.2	$	4.7	$	9.4

Gas Inventory


	March 31,				December 31,
Gas Inventory (millions)	2024		2023		2023
Natural Gas	$	—	$	0.4	$	0.3
Propane		0.2		0.3		0.3
Liquefied Natural Gas & Other		0.1		0.1		0.4
Total Gas Inventory	$	0.3	$	0.8	$	1.0

Utility Plant

Leases

Regulatory Accounting


	March 31,				December 31,
Regulatory Assets consist of the following (millions)	2024		2023		2023
Retirement Benefits	$	27.4	$	28.0	$	29.8
Energy Supply and Other Rate Adjustment Mechanisms		62.3		63.3		52.4
Deferred Storm Charges		7.8		7.7		9.2
Environmental		6.2		6.2		6.1
Income Taxes		0.9		1.6		1.1
Other Deferred Charges		12.6		11.2		11.0
Total Regulatory Assets		117.2		118.0		109.6
Less: Current Portion of Regulatory Assets(1)		65.1		66.4		56.5
Regulatory Assets – noncurrent	$	52.1	$	51.6	$	53.1

(1)

Reflects amounts included in the Accrued Revenue on the Company’s Consolidated Balance Sheets.


	March 31,				December 31,
Regulatory Liabilities consist of the following (millions)	2024		2023		2023
Income Taxes (Note 8)	$	37.9	$	40.3	$	38.6
Rate Adjustment Mechanisms & Other		14.0		12.9		9.3
Total Regulatory Liabilities		51.9		53.2		47.9
Less: Current Portion of Regulatory Liabilities		17.9		17.0		13.5
Regulatory Liabilities – noncurrent	$	34.0	$	36.2	$	34.4

Derivatives

Investments in Marketable Securities


	March 31,				December 31,
Fair Value of Marketable Securities (millions)	2024		2023		2023
Money Market Funds	$	2.0	$	5.7	$	2.0
Fixed Income Funds		3.9		—		4.0
Total Marketable Securities	$	5.9	$	5.7	$	6.0


	March 31,				December 31,
Fair Value of Marketable Securities (millions)	2024		2023		2023
Equity Funds	$	1.6	$	0.8	$	1.1
Fixed Income Funds		0.1		—		0.1
Money Market Funds		0.1		0.1		0.1
Total Marketable Securities	$	1.8	$	0.9	$	1.3

Energy Supply Obligations


	March 31,				December 31,
Energy Supply Obligations (millions)	2024		2023		2023
Current:
Exchange Gas Obligation	$	1.9	$	4.0	$	6.4
Renewable Energy Portfolio Standards		5.1		6.6		8.6
Total Energy Supply Obligations	$	7.0	$	10.6	$	15.0

Subsequent Events

INCOME TAXES - Differences Between Provisions for Income Taxes and Provisions Calculated at Statutory Federal Tax Rate (Detail)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Tax Examination [Line Items]
Statutory Federal Income Tax Rate	21.00%	21.00%
State Income Taxes, net	6.00%	6.00%
Utility Plant Differences	(1.00%)	(1.00%)
Effective Income Tax Rate	26.00%	26.00%

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Mar. 31, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($) Subsidiary mi	Dec. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)
Significant Accounting Policies [Line Items]
Number of Subsidiaries \| Entity \| Subsidiary	3
Length of Pipeline \| mi	85
Cost of removal obligation	$ 130.6	$ 126.3	$ 120.0
Investments in trading securities	5.9	6.0	5.7
Allowance for doubtful accounts	2.8	2.4	3.1
Regulatory assets	117.2	109.6	118.0
Other Deferred Charges [Member]
Significant Accounting Policies [Line Items]
Regulatory assets	12.6	11.0	11.2
Unbilled Revenues [member]
Significant Accounting Policies [Line Items]
Allowance for doubtful accounts	0.1	0.1	0.1
Accounts Receivable [member]
Significant Accounting Policies [Line Items]
Allowance for doubtful accounts	$ 2.7	2.3	3.0
Utilities
Significant Accounting Policies [Line Items]
Number of Subsidiaries \| Entity \| Subsidiary	3
Unitil Service; Unitil Realty; and Unitil Resources
Significant Accounting Policies [Line Items]
Number of Subsidiaries \| Entity \| Subsidiary	3
Fitchburg Gas And Electric Light Company [Member] \| Other Deferred Charges [Member] \| Electric And Gas Division [Member]
Significant Accounting Policies [Line Items]
Hardship accounts in regulatory assets	$ 6.9	6.0	5.8
Environmental and Rate Case Costs and Other Expenditures \| Recovered over the next seven years
Significant Accounting Policies [Line Items]
Regulatory assets	6.9
ISO-NE Obligations
Significant Accounting Policies [Line Items]
Cash Deposits	$ 3.1	3.3	4.2
Maximum
Significant Accounting Policies [Line Items]
Lease term	12 months
Deferred Compensation Plan [Member]
Significant Accounting Policies [Line Items]
Investments in trading securities	$ 1.8	$ 1.3	$ 0.9

Retirement Benefit obligations

3 Months Ended

Mar. 31, 2024

Retirement Benefits [Abstract]

Retirement Benefit obligations

Note 9: Retirement Benefit obligations

The Company co-sponsors the Unitil Corporation Retirement Plan (Pension Plan), the Unitil Retiree Health and Welfare Benefits Plan (PBOP Plan), and the Unitil Corporation SERP to provide certain pension and postretirement benefits for its retirees and current employees. Please see Note 9 to the Consolidated Financial Statements in the Company’s Form 10-K for the year ended December 31, 2023 as filed with the SEC on February 13, 2024 for additional information regarding these plans.

The following table includes the key weighted average assumptions used in determining the Company’s benefit plan costs and obligations:


Used to Determine Plan Costs	2024			2023
Discount Rate		5.00	%		5.25	%
Rate of Compensation Increase		3.00	%		3.00	%
Expected Long-term rate of return on plan assets		7.50	%		7.50	%

The health care cost trend rate used to determine benefit plan costs for 2024 for pre-65 retirees is 8.00%, with an ultimate rate of 4.50% in 2033, and for post-65 retirees, the health care cost trend rate is 6.00%, with an ultimate rate of 4.50% in 2033. The health care cost trend rate used to determine benefit plan costs for 2023 for pre-65 retirees was 8.00%, with an ultimate rate of 4.50% in 2030, and for post-65 retirees, the health care cost trend rate was 6.25%, with an ultimate rate of 4.50% in 2030.

The following tables provide the components of the Company’s Retirement plan costs ($000’s):


	Pension Plan						PBOP Plan						SERP
For the Three Months Ended March 31,	2024			2023			2024			2023			2024			2023
Service Cost	$	497		$	523		$	497		$	373		$	54		$	63
Interest Cost		1,886			1,870			817			725			181			188
Expected Return on Plan Assets		(2,649	)		(2,672	)		(969	)		(852	)		—			—
Prior Service Cost Amortization		81			89			—			198			2			14
Actuarial Loss Amortization		362			—			(219	)		(366	)		—			0
Sub-total		177			(190	)		126			78			237			265
Amounts Capitalized and Deferred		108			498			124			221			(73	)		(82	)
Net Periodic Benefit Cost Recognized	$	285		$	308		$	250		$	299		$	164		$	183

Employer Contributions

As of March 31, 2024, the Company had not made any contributions to its Pension Plan and PBOP Plan, respectively, in 2024. The Company, along with its subsidiaries, expects to make contributions to its Pension and PBOP Plans in 2024 and future years at minimum required and discretionary funding levels consistent with the amounts recovered in the distribution utilities’ rates for these Pension and PBOP Plan costs.

As of March 31, 2024, the Company had made $0.2 million of benefit payments under the SERP Plan in 2024. The Company presently anticipates making an additional $0.5 million of benefit payments under the SERP Plan in 2024.

- Definition

The entire disclosure for retirement benefits.

+ References

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+ Details

DIVIDENDS DECLARED PER SHARE (Detail) - $ / shares	3 Months Ended
DIVIDENDS DECLARED PER SHARE (Detail) - $ / shares	Mar. 31, 2024	Mar. 31, 2023
Dividends Payable [Line Items]
Dividend Amount	$ 0.425	$ 0.405
Group One
Dividends Payable [Line Items]
Declaration Date	May 01, 2024
Date Paid (Payable)	May 31, 2024
Shareholder of Record Date	May 16, 2024
Dividend Amount	$ 0.425
Group Two
Dividends Payable [Line Items]
Declaration Date	Jan. 31, 2024
Date Paid (Payable)	Feb. 29, 2024
Shareholder of Record Date	Feb. 14, 2024
Dividend Amount	$ 0.425
Group Three
Dividends Payable [Line Items]
Declaration Date	Oct. 23, 2023
Date Paid (Payable)	Nov. 28, 2023
Shareholder of Record Date	Nov. 14, 2023
Dividend Amount	$ 0.405
Group Four
Dividends Payable [Line Items]
Declaration Date	Jul. 26, 2023
Date Paid (Payable)	Aug. 28, 2023
Shareholder of Record Date	Aug. 14, 2023
Dividend Amount	$ 0.405
Group Five
Dividends Payable [Line Items]
Declaration Date	Apr. 26, 2023
Date Paid (Payable)	May 30, 2023
Shareholder of Record Date	May 15, 2023
Dividend Amount	$ 0.405
Group Six
Dividends Payable [Line Items]
Declaration Date	Jan. 25, 2023
Date Paid (Payable)	Feb. 28, 2023
Shareholder of Record Date	Feb. 14, 2023
Dividend Amount	$ 0.405

EQUITY - Restricted Stock Units Issued (Detail) - Restricted Stock Units (RSUs)	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Restricted Stock Units
Beginning Restricted Stock Units \| shares	33,375
Restricted Stock Units Granted \| shares	0
Dividend Equivalents Earned \| shares	278
Restricted Stock Units Settled \| shares	0
Ending Restricted Stock Units \| shares	33,653
Weighted-Average Stock Price
Beginning Restricted Stock Units \| $ / shares	$ 42.73
Restricted Stock Units Granted \| $ / shares	0
Dividend Equivalents Earned \| $ / shares	50.96
Restricted Stock Units Settled \| $ / shares	0
Ending Restricted Stock Units \| $ / shares	$ 42.8

Segment Information - Significant Segment Financial Data (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Operating Revenues	$ 178.7	$ 220.2
Segment Profit (Loss)	27.2	24.1
Capital Expenditures	20.2	22.2
Segment Assets	1,697.9	1,614.7	$ 1,670.4
Billed and Unbilled Revenue
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Operating Revenues	171.4	219.5
Rate Adjustment Mechanism Revenue
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Operating Revenues	7.3	0.7
Gas Segment
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Operating Revenues	105.1	112.0
Segment Profit (Loss)	22.4	19.0
Capital Expenditures	10.7	11.5
Segment Assets	1,043.7	979.2
Gas Segment \| Billed and Unbilled Revenue
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Operating Revenues	100.4	121.9
Gas Segment \| Rate Adjustment Mechanism Revenue
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Operating Revenues	4.7	(9.9)
Electric
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Operating Revenues	73.6	108.2
Segment Profit (Loss)	4.9	5.3
Capital Expenditures	8.7	10.6
Segment Assets	625.5	613.7
Electric \| Billed and Unbilled Revenue
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Operating Revenues	71.0	97.6
Electric \| Rate Adjustment Mechanism Revenue
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Operating Revenues	2.6	10.6
All Other Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment Profit (Loss)	(0.1)	(0.2)
Capital Expenditures	0.8	0.1
Segment Assets	$ 28.7	$ 21.8

Components of Exchange Gas Receivable (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Receivables [Line Items]
Total Exchange Gas Receivable	$ 2.2	$ 9.4	$ 4.7
Northern Utilities Inc
Receivables [Line Items]
Total Exchange Gas Receivable	1.9	8.6	4.0
Fitchburg
Receivables [Line Items]
Total Exchange Gas Receivable	$ 0.3	$ 0.8	$ 0.7

INCOME TAXES (Tables)

3 Months Ended

Mar. 31, 2024

Income Tax Disclosure [Abstract]

Differences Between Provisions for Income Taxes and Provisions Calculated at Statutory Federal Tax Rate

The differences between the Company’s provisions for Income Taxes and the provisions calculated at the statutory federal tax rate, expressed in percentages, are shown in the following table:


	For the Three Months Ended March 31,
	2024			2023
Statutory Federal Income Tax Rate		21	%		21	%
Income Tax Effects of:
State Income Taxes, net		6			6
Utility Plant Differences		(1	)		(1	)
Effective Income Tax Rate		26	%		26	%

EQUITY - Additional Information (Detail) - USD ($)		3 Months Ended		12 Months Ended
EQUITY - Additional Information (Detail) - USD ($)	Jan. 30, 2024	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	May 01, 2024
Class of Stock [Line Items]
Common stock, shares outstanding		16,167,887	16,086,230	16,116,724
Common stock, shares issued		5,803	5,335
Proceeds from Issuance of Common Stock		$ 300,000	$ 300,000
Restricted Stock Units Granted		$ 47.72	$ 48.02
Share based compensation expense		$ 1,000,000	$ 1,100,000
Percentage of fully-vested restricted stock units that directors will receive in common shares when settled		70.00%
Percentage of fully-vested restricted stock units that directors will receive in cash when settled		30.00%
Preferred Stock		$ 200,000	200,000	$ 200,000
Maximum
Class of Stock [Line Items]
Dividend declared		$ 100,000	$ 100,000
Restricted Stock
Class of Stock [Line Items]
Restricted stock vesting period		4 years
Restricted stock non-vested		59,163	64,243
Fair value of liabilities associated with fully vested RSUs that will be settled in cash		$ 800,000	$ 1,100,000	$ 800,000
Unrecognized share based compensation		$ 1,200,000
Share compensation recognition period		2 years 9 months 18 days
Restricted Stock Units Granted	22,680
Aggregate Market Value	$ 1,100,000
Forfeitures under the stock plan		0
Cancellations under the stock plan		0
Restricted Stock \| Maximum
Class of Stock [Line Items]
Restricted stock available for awards		677,500			1,027,500
Restricted stock that may be awarded in any one calendar year to any one participant		20,000
Restricted Stock \| Vesting Annually
Class of Stock [Line Items]
Restricted stock vesting percentage annually		25.00%
Restricted Stock Units (RSUs)
Class of Stock [Line Items]
Restricted Stock Units Granted		0
Restricted stock units outstanding			44,125
Weighted-Average Stock Price			$ 40.27
Performance Shares [Member]
Class of Stock [Line Items]
Restricted stock non-vested		43,453
Restricted Stock Units Granted		$ 50.35
Share based compensation expense		$ 200,000	$ 100,000
Unrecognized share based compensation		$ 2,200,000
Share compensation recognition period		2 years 3 months 18 days
Restricted Stock Units Granted	22,680
Aggregate Market Value	$ 1,100,000
Forfeitures under the stock plan		0
Cancellations under the stock plan		0
Series 6 \| Unitil Energy Systems Inc
Class of Stock [Line Items]
Preferred stock, outstanding		1,727	1,861	1,727
Preferred Stock		$ 200,000	$ 200,000	$ 200,000
Dividend rate		6.00%	6.00%	6.00%
Dividend and Distribution Reinvestment and Share Purchase Plan
Class of Stock [Line Items]
Proceeds from Issuance of Common Stock		$ 291,200
Dividend and Distribution Reinvestment and Share Purchase Plan \| Average
Class of Stock [Line Items]
Common stock price per share		$ 50.17
Dividend and Distribution Reinvestment and Share Purchase Plan \| Common Stock
Class of Stock [Line Items]
Common stock, shares issued		5,803

DEBT AND FINANCING ARRANGEMENTS - Details On Long Term Debt (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Debt Instrument [Line Items]
Total Long-Term Debt	$ 516.0	$ 517.2	$ 497.9
Less: Unamortized Debt Issuance Costs	3.2	3.2	3.2
Long-Term Debt	512.8	514.0	494.7
Less: Current Portion	4.9	4.9	6.7
Total Long-Term Debt, Less Current Portion	507.9	509.1	488.0
3.70% Senior Notes, Due August 1, 2026
Debt Instrument [Line Items]
Total Long-Term Debt	30.0	30.0	30.0
3.43% Senior Notes, Due December 18, 2029
Debt Instrument [Line Items]
Total Long-Term Debt	30.0	30.0	30.0
Unitil Energy Systems Inc \| First Mortgage Bonds 6.96% Senior Secured Notes, Due September 1, 2028
Debt Instrument [Line Items]
Total Long-Term Debt	10.0	10.0	12.0
Unitil Energy Systems Inc \| First Mortgage Bonds 8.00% Senior Secured Notes, Due May 1, 2031
Debt Instrument [Line Items]
Total Long-Term Debt	12.0	12.0	13.5
Unitil Energy Systems Inc \| First Mortgage Bonds 6.32% Senior Secured Notes, Due September 15, 2036
Debt Instrument [Line Items]
Total Long-Term Debt	15.0	15.0	15.0
Unitil Energy Systems Inc \| First Mortgage Bonds 3.58% Senior Secured Notes, Due September 15, 2040
Debt Instrument [Line Items]
Total Long-Term Debt	27.5	27.5	27.5
Unitil Energy Systems Inc \| First Mortgage Bonds 4.18% Senior Secured Notes Due November 30, 2048
Debt Instrument [Line Items]
Total Long-Term Debt	30.0	30.0	30.0
Fitchburg Gas and Electric Light Company \| 6.79% Senior Notes, Due October 15, 2025
Debt Instrument [Line Items]
Total Long-Term Debt	0.0	0.0	2.0
Fitchburg Gas and Electric Light Company \| 3.52% Senior Notes, Due November 1, 2027
Debt Instrument [Line Items]
Total Long-Term Debt	10.0	10.0	10.0
Fitchburg Gas and Electric Light Company \| 7.98% Notes, Due June 1, 2031
Debt Instrument [Line Items]
Total Long-Term Debt	14.0	14.0	14.0
Fitchburg Gas and Electric Light Company \| 7.37% Notes, Due January 15, 2029
Debt Instrument [Line Items]
Total Long-Term Debt	6.0	7.2	7.2
Fitchburg Gas and Electric Light Company \| 5.90% Notes, Due December 15, 2030
Debt Instrument [Line Items]
Total Long-Term Debt	15.0	15.0	15.0
Fitchburg Gas and Electric Light Company \| 5.70% Notes, Due July 2, 2033
Debt Instrument [Line Items]
Total Long-Term Debt	12.0	12.0	0.0
Fitchburg Gas and Electric Light Company \| 5.96% Senior Notes, Due July 2, 2053
Debt Instrument [Line Items]
Total Long-Term Debt	13.0	13.0	0.0
Fitchburg Gas and Electric Light Company \| 3.78% Senior Notes, Due September 15, 2040
Debt Instrument [Line Items]
Total Long-Term Debt	27.5	27.5	27.5
Fitchburg Gas and Electric Light Company \| 4.32% Senior Notes, Due November 1, 2047
Debt Instrument [Line Items]
Total Long-Term Debt	15.0	15.0	15.0
Northern Utilities Inc \| 3.52% Senior Notes, Due November 1, 2027
Debt Instrument [Line Items]
Total Long-Term Debt	20.0	20.0	20.0
Northern Utilities Inc \| 7.72% Senior Notes, Due December 3, 2038
Debt Instrument [Line Items]
Total Long-Term Debt	50.0	50.0	50.0
Northern Utilities Inc \| 3.78% Senior Notes, Due September 15, 2040
Debt Instrument [Line Items]
Total Long-Term Debt	40.0	40.0	40.0
Northern Utilities Inc \| 4.42% Senior Notes, Due October 15, 2044
Debt Instrument [Line Items]
Total Long-Term Debt	50.0	50.0	50.0
Northern Utilities Inc \| 4.32% Senior Notes, Due November 1, 2047
Debt Instrument [Line Items]
Total Long-Term Debt	30.0	30.0	30.0
Northern Utilities Inc \| 4.04% Senior Notes, Due September 12, 2049
Debt Instrument [Line Items]
Total Long-Term Debt	40.0	40.0	40.0
Granite State Gas Transmission Inc \| 3.72% Senior Notes, Due November 1, 2027
Debt Instrument [Line Items]
Total Long-Term Debt	15.0	15.0	15.0
Unitil Realty Corp [Member] \| 2.64% Senior Secured Notes, Due December 18, 2030
Debt Instrument [Line Items]
Total Long-Term Debt	$ 4.0	$ 4.0	$ 4.2

Regulatory Matters

3 Months Ended

Mar. 31, 2024

REGULATORY MATTERS

note 6 - REgulatory Matters

Unitil’s Regulatory matters are described in Note 8 to the Financial Statements in Item 8 of Part II of Unitil Corporation’s Form 10-K for December 31, 2023 as filed with the Securities and Exchange Commission on february 13, 2024.

Rate Case Activity

Northern Utilities - Base Rates - Maine - On September 20, 2023, the MPUC issued an order approving a Stipulation filed on August 31, 2023, between Northern Utilities and the Office of the Public Advocate which resolved all matters in the base rate filing made by Northern Utilities with the MPUC on May 1, 2023. The order approves an increase in distribution revenues of $7.6 million effective October 1, 2023. The order reflects a return on equity of 9.35%, an equity ratio of 52.01%, and a weighted average cost of capital of 7.22%.

Northern Utilities - Targeted Infrastructure Replacement Adjustment (TIRA) - Maine -

The settlement in Northern Utilities’ Maine division’s 2013 rate case authorized the Company to implement a TIRA rate mechanism to adjust base distribution rates annually to recover the revenue requirements associated with targeted investments in gas distribution system infrastructure replacement and upgrade projects, including the Company’s Cast Iron Replacement Program (CIRP). In its Final Order issued on February 28, 2018 for Northern Utilities’ 2017 base rate case, the MPUC approved an extension of the TIRA mechanism for an additional eight-year period, which will allow for annual rate adjustments through the end of the CIRP program. The Company’s most recent request under the TIRA mechanism, to increase annual base rates by $2.4 million for 2023 eligible facilities, was filed with the MPUC on April 24, 2024. On April 30, 2024, the MPUC issued an order approving the filing, for rates effective May 1, 2024.

Northern Utilities - Base Rates - New Hampshire - On July 20, 2022, the NHPUC issued an Order in the distribution base rate case filed with the NHPUC on August 2, 2021 by Northern Utilities. The Order approved a comprehensive Settlement Agreement between the Company, the New Hampshire Department of Energy (DOE), and the Office of the Consumer Advocate (OCA). As provided in the Settlement Agreement, in addition to authorizing an increase to permanent distribution rates of $6.1 million, effective August 1, 2022, the Order (1) approved a revenue decoupling mechanism and (2) allowed for a step adjustment effective September 1, 2022 covering the additional revenue requirement resulting from changes in Net Plant in Service associated with non-growth investments for the period January 1, 2021, through December 31, 2021. This distribution base rate case reflected the Company’s operating costs and investments in utility plant for a test year ended December 31, 2020 as adjusted for known and measurable changes. The Order provided for a return on equity of 9.3% and a capital structure reflecting 52% equity and 48% long-term debt. The increase in permanent rates was reconciled back to October 1, 2021, the effective date of temporary rates previously approved in this docket. On June 8, 2022, the Company filed for its step increase of approximately $1.6 million of annual revenue, for rates effective as of September 1, 2022, to recover eligible 2021 capital investments. On August 31, 2022, the NHPUC approved the Company’s filing.

Unitil Energy - Base Rates - On May 3, 2022, the NHPUC issued an Order in the distribution base rate case filed with the NHPUC on April 2, 2021 by Unitil Energy. The Order approved, in part, a comprehensive Settlement Agreement between the Company, the New Hampshire DOE, the OCA, the New Hampshire Department of Environmental Services, Clean Energy New Hampshire, and ChargePoint, Inc. In addition to authorizing an increase to permanent distribution rates of $6.3 million, effective June 1, 2022, the Order approved the following components of the Settlement Agreement: (1) a multi-year rate plan, (2) a revenue decoupling mechanism, (3) time-of-use rates, (4) resiliency programs to support the Company’s commitment to reliability, and (5) other rate design and tariff changes. On May 10, 2022, the Company filed a request for clarification with the NHPUC to clarify that the authorized revenue requirement should exclude expenses related to the Company’s proposed Arrearage Management Program (AMP), which was not approved in the Order. On May 12, 2022, the Commission issued an Order, which clarified that because the Company will not incur the expenses associated with the AMP, those costs should be removed from the revenue requirement, and that the adjusted increase of $5.9 million will result in reasonable rates. The increase in permanent rates was reconciled back to June 1, 2021, the effective date of temporary rates previously approved in this docket. This distribution base rate case reflected the Company’s operating costs and investments in utility plant for a test year ended December 31, 2020 as adjusted for known and measurable changes. The Order provided for a return on equity of 9.2% and a capital structure reflecting 52% equity and 48% long-term debt. On July 28, 2022, the NHPUC approved the Company’s first step increase of approximately $1.3 million of annual revenue to recover eligible 2021 capital investments, effective August 1, 2022. On May 31, 2023, the NHPUC approved the Company’s second and final step adjustment increase of approximately $1.2 million to recover eligible 2022 capital investments, effective June 1, 2023.

Fitchburg - Base Rates - Electric- Fitchburg’s base rates are decoupled and subject to an annual revenue decoupling adjustment mechanism, which includes a cap on the amount that rates may be increased in any year. In addition, Fitchburg has an annual capital cost recovery mechanism to recover the revenue requirement associated with certain capital additions. On July 26, 2023, the MDPU issued an Order approving the Company's cumulative revenue requirement of $3.1 million associated with its 2019-2021 capital expenditures. On November 1, 2023, Fitchburg filed its cumulative revenue requirement of $3.6 million associated with its 2019-2022 capital expenditures. On November 27, 2023, Fitchburg revised its cumulative revenue requirement to $3.5 million. On December 22, 2023, the MDPU allowed the associated rate increase to become effective on January 1, 2024, subject to further investigation and reconciliation.

On August 17, 2023, Fitchburg filed a petition with the MDPU seeking approval for a $6.8 million increase to base distribution rates, with new rates anticipated to be effective July 1, 2024. Fitchburg proposes to transfer $2.7 million in revenue requirements recovered through certain reconciling mechanisms to base distribution rates. Net of these transfers, the proposed overall increase to distribution revenues is $4.1 million. As part of this filing, Fitchburg is requesting approval for a performance-based ratemaking (PBR) plan for up to a five-year term and continuation of its revenue decoupling mechanism. A decision from the MDPU is expected in June 2024.

Fitchburg - Base Rates - Gas - On August 17, 2023, Fitchburg filed a petition with the MDPU seeking approval for a $10.9 million increase to base distribution rates, with new rates anticipated to be effective July 1, 2024. Fitchburg proposes to transfer $4.2 million in revenue requirements recovered through its Gas System Enhancement Program to base distribution rates. Net of these transfers, the proposed overall increase to distribution revenues is $6.7 million. As part of this filing, Fitchburg is requesting approval for a PBR plan for up to a five-year term and continuation of its revenue decoupling mechanism. A decision from the MDPU is expected in June 2024.

Fitchburg - Gas System Enhancement Program- Pursuant to statute and MDPU order, Fitchburg has an approved Gas System Enhancement Plan tariff through which it may recover certain gas infrastructure replacement and safety related investment costs, subject to an annual cap. Under the plan, the Company is required to make two annual filings with the MDPU: a forward-looking

filing for the subsequent construction year, to be filed on or before October 31; and a filing, submitted on or before May 1, of final project documentation for projects completed during the prior year, demonstrating substantial compliance with its plan in effect for that year and showing that project costs were reasonably and prudently incurred. Fitchburg’s forward-looking cumulative revenue requirement filing submitted on October 31, 2022 requested recovery of approximately $4.5 million, and received final approval on April 28, 2023, effective May 1, 2023. The Company’s most recent forward-looking cumulative revenue requirement filing, filed on October 31, 2023, requested recovery of approximately $6.4 million. On April 30, 2024, the MDPU issued an order approving this filing for rates effective May 1, 2024.

Granite State - Base Rates - On November 30, 2020, the FERC approved Granite State’s filing of an uncontested rate settlement which provided for an increase in annual revenues of approximately $1.3 million, effective November 1, 2020. The Settlement Agreement permits the filing of limited Section 4 rate adjustments for capital cost projects eligible for cost recovery in 2021, 2022, and 2023, and sets forth an overall investment cap of approximately $14.6 million on the capital cost recoverable under such filings during the term of the Settlement. Under the Settlement Agreement, Granite may not file a new general rate case earlier than April 30, 2024 with rates to be effective no earlier than November 1, 2024 based on a test year ending no earlier than December 31, 2023.

On August 24, 2021, the FERC accepted Granite State’s first limited Section 4 rate adjustment pursuant to the Settlement Agreement, for an annual revenue increase of $0.1 million, effective September 1, 2021. On August 19, 2022, the FERC accepted Granite State’s second limited Section 4 rate adjustment pursuant to the Settlement Agreement, for an annual revenue increase of $0.3 million, effective September 1, 2022. On July 27, 2023, Granite State filed its third and final limited Section 4 rate adjustment pursuant to the Settlement Agreement, for an annual revenue increase of $1.0 million, effective September 1, 2023. On August 22, 2023, the FERC approved this filing.

Other Matters

Unitil Energy - Proposal to Construct Utility-Scale Solar Facility - On October 31, 2022, Unitil Energy submitted a petition to the NHPUC for review of Unitil Energy’s proposal to construct, own, and operate a 4.99 MW utility-scale photovoltaic generating facility, which was subsequently revised to a 4.88 MW facility. On May 1, 2023, the NHPUC issued an Order approving the Company's petition.

On February 5, 2024, the NH Department of Environmental Services (“NHDES”) issued an Alteration of Terrain Permit for the project. On February 9, 2024, NHDES issued a Wetland and Non-Site Specific Permit for the project. On February 14, 2024, the United States Army Corps of Engineers issued a NH General Permit for the project. The Company has commenced site work for the project.

Unitil Energy - Major Storm Cost Reserve Recovery -On April 26, 2024 Unitil Energy filed a request with the NHPUC to increase its Storm Reserve Adjustment Factor effective June 1, 2024. The increase would allow the Company to recover the under-collected Major Storm Cost Reserve (MSCR) balance as of December 31, 2023 of approximately $3.7 million plus $0.2 million of projected carrying costs over a three-year period. This matter remains pending.

Fitchburg - Grid Modernization - On July 1, 2021, Fitchburg submitted its Grid Modernization Plan (GMP) to the MDPU. The GMP includes a five-year strategic plan, including a plan for the full deployment of advanced metering functionality, and a four-year short-term investment plan, which focuses on foundational investments to facilitate the interconnection and integration of distributed energy resources, optimizing system performance through command and control and self-healing measures, and optimizing system demand by facilitating consumer price-responsiveness. On October 7, 2022, the MDPU issued a “Track 1” Order approving a budget cap of $9.3 million through 2025 for previously deployed or preauthorized grid modernization investments. On November 30, 2022, the MDPU issued its “Track 2” Order addressing new technologies and Advanced Metering Infrastructure (AMI) proposals. The MDPU preauthorizes a four-year $1.5 million budget for Fitchburg’s additional grid-facing investments. Any spending over the total budget cap is not eligible for targeted cost recovery through its Grid Modernization Factor (GMF), and instead, may be recovered by the Company in a base distribution rate proceeding subsequent to a prudency finding by the MDPU in a GMF filing or term review Order. The MDPU also preauthorized the Company’s AMI meter replacement investments, with a budget of $11.2 million through 2025. Additionally, the MDPU provided preliminary approval for the Company’s customer engagement and experience and data sharing platform investments, with a combined budget of $2.3 million through 2025. The Company may recover eligible costs incurred for preauthorized grid-facing investments and customer-facing investments that will be made during the 2022-2025 GMP term through the GMFs, subject to certain modifications to the Company’s GMF tariff and a final prudence review. On March 31, 2023, the Company submitted an AMI opt-out tariff with full support of proposed opt-out fees in compliance with the Track 2 Order. The MDPU approved the tariff on April 7, 2023.

On April 24, 2023, Fitchburg submitted its 2022 Grid Modernization Plan Annual Report to the MDPU. Among other things, the Company explained a modification to its implementation of the AMI plan that the MDPU preauthorized in D.P.U. 21-82. Due to a

discontinuation of the meter technology upon which the Company’s initial AMI plan relied, the Company reported that it will need to replace its meters with a new meter technology and to implement a new communications system. On May 31, 2023, the MDPU issued an Order indicating its intent to explore the impact of the discontinuation and determine the appropriate next steps outside the GMF proceeding. On April 15, 2024, the Company submitted its annual Grid Modernization Filing seeking recovery of costs related to grid modernization investments placed into service in 2023. In connection with this filing, the Company submitted a request for preauthorization of communications systems and head end system investments that will be implemented in connection with the Company’s advanced metering infrastructure replacement project. The matter remains pending.

Fitchburg - Grid Modernization Cost Recovery Factor - On April 15, 2023, Fitchburg filed its GMF rate adjustment and reconciliation filing for recovery of the costs incurred as a result of implementing the Company’s 2022-2025 GMP, approved by the MDPU in Orders dated October 7, 2022 and November 30, 2022. On May 31, 2023, the MDPU approved, subject to further investigation and reconciliation, the cumulative recovery of $1.0 million associated with the Company’s 2022 GMP revenue requirement, effective June 1, 2023. The MDPU conducted a hearing on September 26, 2023 regarding the Company’s pending GMF filings and Grid Modernization Term Report. The matter remains pending. On April 15, 2024, Fitchburg filed its GMF rate adjustment and reconciliation filing for recovery of the costs incurred as a result of implementing the Company’s 2022-2025 GMP. This filing seeks recovery of $1.3 million associated with its 2023 revenue requirement, effective June 1, 2024. This matter remains pending.

Fitchburg - Investigation into the role of gas LDCs to achieve Commonwealth 2050 climate goals - The MDPU has opened an investigation to examine the role of Massachusetts gas local distribution companies (LDCs) in helping the Commonwealth achieve its 2050 climate goal of net-zero greenhouse gas (GHG) emissions. In its Order opening the inquiry, the MDPU stated it is required to consider new policies and structures as the Commonwealth reduces reliance on fossil fuels, including natural gas, which may require LDCs to make significant changes to their planning processes and business models. The LDCs, including Fitchburg, engaged an independent consultant to conduct a study and prepare a report (Consultant Report), including a detailed study of each LDC, that analyzes the feasibility of all identified pathways to help the Commonwealth achieve its net-zero GHG goal. The study includes an examination of the potential pathways identified in the 2050 Decarbonization Roadmap developed by the MA Executive Office of Energy and Environmental Affairs, in consultation with the Massachusetts Department of Environmental Protection and the Massachusetts Department of Energy Resources (DOER).

On December 6, 2023, the MDPU issued an Order announcing a regulatory framework intended to set forth its role and that of the LDCs in helping the Commonwealth achieve its target of net-zero GHG emissions by 2050. In this proceeding, the MDPU reviewed eight potential decarbonization “pathways” and six regulatory design recommendations intended to facilitate the Commonwealth’s transition. The MDPU made no specific findings as to a preferred pathway or technology, but did make specific findings regarding regulatory design recommendations. The MDPU instructed the LDCs in their next rate case to revise their per-customer revenue decoupling mechanism to a decoupling approach based on total revenues. The MDPU emphasized that the Order is not intended to jeopardize the rate recovery of existing investments in natural gas infrastructure by Fitchburg. As part of future cost recovery proposals, LDCs will bear the burden of demonstrating that non-gas pipeline alternatives (NPAs) were adequately considered and found to be non-viable or cost prohibitive to receive full cost recovery of investments. The MDPU further found that the “clean energy transition” will require coordinated planning between LDCs and electric distribution companies, monitoring progress through LDC reporting, and aligning existing MDPU practices with climate targets. To that end, the MDPU ordered the LDCs to submit individual Climate Compliance Plans every five years beginning in 2025, and to propose climate compliance performance metrics in upcoming performance-based regulation filings, ensuring a proactive approach to achieving climate targets.

On December 29, 2023, the LDCs filed a Joint Motion for Clarification and Extension of Judicial Appeal Period. The Joint Motion requests clarification of three issues: (1) the MDPU’s directive concerning the NPAs analysis; (2) the timetable for establishing ‘incentives and disincentives’ for progress toward compliance with Climate Act mandates as part of a PBR framework and achievement of approved Climate Compliance Plans; and (3) the methodology for emissions reduction accounting for Climate Compliance Plans, with particular attention to Scope 1 and Scope 3 emissions accounting. On April 2, 2024, the Commission issued an Order on the LDCs’ Joint Motion. In its Order, the MDPU clarified, among other things, that NPA analyses should be applied at the project level to all investment decisions going forward, and should be considered at project planning stage; that pending an approved NPA framework, LDCs should make all reasonable efforts to incorporate NPA analyses into investment decisions; and that LDCs will have the burden to demonstrate the prudence of implementing a traditional project instead of a NPA. The MDPU did not expressly exempt any category of project from the NPA analysis requirement.

Fitchburg - Electric Sector Modernization Plan- Pursuant to M.G.L. c. 164 § 92B, Fitchburg submitted a draft Electric Sector Modernization Plan (ESMP) to the statutorily created Massachusetts Grid Modernization Advisory Council (Council) for the Council’s review, input, and recommendations. The ESMP is a plan intended to upgrade the Company’s distribution system to enable and accommodate increased distributed energy resources and electrification technologies, improve grid reliability and resiliency, and assist the Commonwealth in achieving climate goals, among other objectives. The Council provided recommendations on the ESMP in November 2023. The Company submitted its final ESMP to the MDPU on January 29, 2024. The Company concurrently submitted

a proposal to recover, among other things, incremental costs associated with ESMP investments through an annual reconciling rate adjustment mechanism. On February 20, 2024, the MDPU issued an interlocutory order finding in part that “to the extent that the MDPU determines that accelerated cost recovery through annual reconciling mechanisms for proposed investments identified in the ESMPs is appropriate, we anticipate establishing the appropriate parameters for those mechanisms through a separate phase of these proceedings to be conducted after August 29, 2024.” This matter remains pending before the MDPU.

Fitchburg - Electric Vehicle (EV) Proceeding - On December 30, 2022, the MDPU issued an order approving Fitchburg’s five-year EV program with a $1.0 million budget consisting of: (1) public infrastructure offering ($0.5 million); (2) Electric Vehicle Supply Equipment (EVSE) incentives for residential segment ($0.3 million); and (3) marketing and outreach ($0.2 million). The Company may shift spending between program segments and between years over the five-year term of its program, subject to a 15% cap. Any spending above the approved EV program budget or above the 15% cap for each program segment is not eligible for targeted cost recovery through the GMF and, instead, may be recovered in a base distribution rate proceeding subsequent to a prudency finding by the MDPU. Further, the MDPU has convened an EV stakeholder process to finalize EV program performance metrics. On April 3, 2023, the electric companies filed comments on the MDPU’s proposed metrics. Once performance metrics are finalized, the MDPU will require the electric companies to develop a joint state-wide program evaluation plan for MDPU approval and stakeholder input and will determine next steps at that time. The MDPU directs the Companies to submit annual reports that document their performance and these reports will be due on or before May 15th of each year. The first EV annual report is due May 15, 2024. The Company shall file annual rate adjustment and reconciliation filings on or before April 15, with rates effective June 1. The MDPU accepted the Company’s Demand Charge Alternative proposal and directed implementation within six months. The Demand Charge Alternative is offered for a ten-year period beginning July 1, 2023 with tiered rates to separately-metered EV general delivery service customers. The MDPU accepted the Company’s proposed residential EV TOU rate, effective April 1, 2023.

Fitchburg - Storm Cost Deferral Petition -On November 2, 2023, Fitchburg filed a request with the MDPU to increase its Storm Reserve Adjustment Factor effective January 1, 2024. The increase would allow the Company to recover approximately $4.8 million of costs of repairing damage to its electrical system plus $1.4 million of projected carrying costs resulting from the January and March 2023 winter storms over a five-year period. On December 19, 2023, the MDPU allowed the associated rate increase to become effective on January 1, 2024, subject to further investigation and reconciliation.

Fitchburg- Approval of Gas Supply Agreement with Constellation LNG- On February 16, 2024, Fitchburg filed a petition with the MDPU for approval of a six year agreement with Constellation LNG for the purchase of natural gas in the liquid or vapor form for the period June 1, 2024 through May 31, 2030 heating seasons. This request is for the approval of two contracts, the first for up to 3,400 Dth per day of natural gas peaking supply to the Company. This first contract will be broken out for 3,000 Dth per Day in the form of LNG for use at the Company’s Westminster LNG facility and 400 Dth per Day will be in the form of natural gas supply delivered to the city-gate connecting the Company’s system to the Tennessee Gas Pipeline. The second contract will provide up to 3,000 Dth per day of LNG trucking from the Everett Marine Terminal to the Company’s Westminster LNG facility.

This proposed agreement would ensure that the Everett Marine Terminal, which plays a critical role in both the Company’s and the New England energy market’s efficient and reliable operation, will continue to be available for the next six winter seasons. A six year agreement was also requested by Boston Gas Company, Eversource Gas Company, and NSTAR Gas Company.

An in-person hearing was held on March 12, 2024 at Everett City Hall and a video conference was held by the MDPU on March 15, 2024. This matter remains pending. Fitchburg and other LDCs have requested an Order by May 1, 2024.

Northern Utilities / Granite State - Firm Capacity Contract - Northern Utilities relies on the transportation of gas supply over its affiliate Granite State pipeline to serve its customers in the Maine and New Hampshire service areas. Granite State facilitates critical upstream interconnections with interstate pipelines and third party suppliers essential to Northern Utilities’ service to its customers. Northern Utilities reserves firm capacity through a contract with Granite State, which is renewed annually. Pursuant to statutory requirements in Maine and orders of the MPUC, Northern Utilities submits an annual informational report requesting approval of a one-year extension of its 12-month contract for firm pipeline capacity reservation, with an evergreen provision and three-month termination notification requirement. On March 29, 2024, Northern Utilities submitted an annual informational report requesting approval on a one-year extension for the period of November 1, 2024 through October 31, 2025. This matter is pending.

Northern Utilities / Portland Natural Gas Transmission System (PNGTS) and TransCanada Pipelines Limited (TCPL) transportation from Empress, Alberta to Granite State Gas Transmission, Inc. (GSGT)

- On October 5, 2023, Northern Utilities filed with the NHPUC and the MPUC a request to approve agreements for the ability for Northern Utilities to increase supply portfolio capacity by 12,500 Dth per day in New Hampshire and Maine. This incremental capacity to Northern Utilities’ supply portfolio took effect April 1, 2024 for a thirty-year term. Northern Utilities was able to acquire this incremental supply of TCPL capacity through an open season process. On January 26, 2024 and January 30, 2024, the Company received orders from the NHPUC and MPUC, respectively, approving Northern Utilities’ proposal for Empress Agreements with PNGTS and TransCanada Pipelines. Conservation Law Foundation filed a motion for reconsideration of the Maine Commission’s decision on February 15, 2024. The Company objected to the motion, which remains pending before the Commission.

Reconciliation Filings - Fitchburg, Unitil Energy and Northern Utilities each have a number of regulatory reconciling accounts that require annual or semi-annual filings with the MDPU, NHPUC and MPUC, respectively, to reconcile revenues and costs, and to seek approval of any rate changes. These filings include: annual electric reconciliation filings by Fitchburg and Unitil Energy for a number of items, including default service, stranded cost changes and transmission charges; costs associated with energy efficiency programs in New Hampshire and Massachusetts, as directed by the NHPUC and MDPU; recovery of the ongoing costs of storm repairs incurred by Unitil Energy and Fitchburg; and the actual wholesale energy costs for electric power and gas incurred by each of the three companies. Fitchburg, Unitil Energy and Northern Utilities have been, and remain in full compliance with all directives and orders regarding these filings. The Company considers these to be routine regulatory proceedings, and there are no material issues outstanding.

Fitchburg - Massachusetts Request for Proposals (RFPs) - Pursuant to Section 83C of “An Act to Promote Energy Diversity” (2016) (the Act), the Massachusetts electric distribution companies (EDCs), including Fitchburg, are required to jointly procure a total of 1,600 MW of offshore wind by June 30, 2027. Under Section 83D of the Act, the EDCs are required to jointly seek proposals for cost-effective clean energy (hydroelectric, solar and land-based wind) long-term contracts via one or more staggered solicitations for a total of 9,450,000 megawatt-hours (MWh) by December 31, 2022. Fitchburg’s pro rata share of these contracts is approximately 1%.

The EDCs issued the RFP for Section 83D Long-Term Contracts in March 2017, and power purchase agreements (PPAs) for 9,554,940 MWh of hydroelectric generation and associated environmental attributes from Hydro-Quebec Energy Services (U.S.), Inc. were filed in July 2018 for approval by the MDPU. On June 25, 2019, the MDPU approved the PPAs, including the EDCs’ proposal to sell the energy procured under the contract into the ISO-NE wholesale market and to credit or charge the difference between the contract costs and the ISO-NE market revenue to customers. The MDPU also approved the EDCs’ request for remuneration equal to 2.75% of the contract payments, as well as the EDCs’ proposal to recover costs associated with the contracts. On January 13, 2023, NECEC Transmission LLC (NECEC), the company with which Fitchburg and the other EDCs entered into transmission service agreements (TSAs) for the delivery of the Hydro-Quebec energy, provided a letter to the EDCs purporting to give notice of a “change in applicable law” related to a Maine ballot initiative and requesting a negotiated amendment to the TSAs including a price adjustment. On June 27, 2023, NECEC sent a letter to the EDCs seeking schedule relief also in accordance with their “change in law” determination. The EDCs are evaluating NECEC’s requests.

Section 83C of “An Act Relative to Green Communities,” St. 2008, c. 169, as amended by St. 2016, c. 188, § 12 (“Section 83C”) requires the EDCs to jointly and competitively solicit proposals for offshore wind energy generation not later than June 30, 2017. The EDCs issued an initial RFP pursuant to Section 83C in June 2017. On July 23, 2018, the EDCs, filed two long-term contracts with Vineyard Wind, each for 400 MW of offshore wind energy generation, for approval by the MDPU. On April 12, 2019, the MDPU approved the offshore wind energy generation PPAs, including the EDCs’ proposal to sell the energy procured under the contract into the ISO-NE wholesale market and to credit or charge the difference between the contract costs and the ISO-NE market revenue to customers. The EDCs issued a second RFP pursuant to Section 83C to procure an additional 800 MW of offshore wind energy generation in May 2019. The EDCs filed for approval of two PPAs with Mayflower Wind Energy LLC (now known as SouthCoast Wind), each for 400 MW of offshore wind energy generation, on February 10, 2020. On November 5, 2020, the MDPU approved the PPAs. In both cases, the MDPU approved the EDCs’ request for remuneration equal to 2.75% of the contract payments, as well as the EDCs’ proposal to recover costs associated with the contracts. In April 2023, SouthCoast Wind engaged with the EDCs to explore options to mitigate impacts of global resource constraints and pricing challenges associated with the PPAs from this procurement. They cited an inability to finance the project within the terms set out in the PPA. The EDCs negotiated a termination agreement with SouthCoast Wind which was filed with the MDPU for approval on August 28, 2023 and which received approval on September 30, 2023.

In accordance with “An Act to Advance Clean Energy” (2018) the Massachusetts Department of Energy Resources (DOER) recommended that the EDCs solicit up to 1,600 MW in additional offshore wind in 2022 and 2024. On May 7, 2021, the EDCs issued a third RFP for up to an additional 1,600 MW of off shore wind generation. On May 25, 2022, the EDCs sought approval of PPAs with Commonwealth Wind for 1,200 MW and with SouthCoast Wind for 400 MW. On December 16, 2022, Commonwealth Wind filed a motion requesting that the MDPU dismiss proceedings related to the approval of its contract, arguing that, due to various economic conditions, its contracts with the EDCs would no longer facilitate the financing of offshore wind energy generation. On December 30, 2022, the MDPU denied Commonwealth’s motion and approved the PPAs. The MDPU also approved the EDCs’ request for remuneration equal to 2.25

% as reasonable and in the public interest. On January 19, 2023, Commonwealth Wind filed a Petition for Appeal with the Massachusetts Supreme Judicial Court seeking to set aside and vacate the MDPU’s Order approving the PPAs. In April 2023, SouthCoast Wind engaged with the EDCs to explore options to mitigate global resource constraints and pricing challenges associated with their PPAs from this procurement. SouthCoast Wind noted challenges around an inability to finance the projects under the current terms. The EDCs negotiated termination agreements with Commonwealth Wind and SouthCoast Wind and submitted the agreements to the MDPU for approval on July 13, 2023 and August 28, 2023, respectively. The MDPU approved both termination agreements on September 30, 2023.

In connection with the termination agreements from the second and third solicitations, the Company received termination payments totaling $1.1 million from Commonwealth Wind and SouthCoast Wind which is recorded as a regulatory liability on the Company’s Consolidated Balance Sheets to be flowed back to customers. On October 12, 2023, Commonwealth Wind requested that the case with the Supreme Court be entered as dismissed. Concurrently, Commonwealth Wind announced publicly they could not finance the project under the terms of the PPA.

In 2021, the MA legislature increased the total solicitation target (including future solicitations) for offshore wind energy generation to 5,600 MW by June 30, 2027. On August 30, 2023, the EDCs issued a fourth offshore wind RFP seeking to procure at least 400 MW and up to the maximum amount remaining of the statutory requirement under Section 83C of 5,600 MW of Offshore Wind Energy Generation, and taking into account offshore wind generation under contract at the time when proposals are due. Bidders are allowed to offer proposals of at least 200 MW up to 2,400 MW of offshore wind generation. On January 18, 2024, the EDCs notified the MDPU that they are extending the bid submission date and subsequent solicitation schedule dates by an additional 56 days each to allow bidders the opportunity to gain more certainty around their eligibility for the investment tax credit and factor it into their proposals. The submission date was revised to March 27, 2024. The EDCs received a number of bids from three separate developers on March 27, 2024, and are engaged in reviewing the bids for completeness and threshold eligibility before moving into quantitative evaluation and qualitative scoring. The selection date is scheduled for August 7, 2024.

Unitil Energy/Northern Utilities - 2024-2026 Triennial Energy Efficiency Plan - New Hampshire - On November 30, 2023, the NHPUC approved the changes to New Hampshire’s ratepayer-funded energy efficiency program offerings for the 2024–2026 period requested by New Hampshire’s electric and gas utilities.

FERC Transmission Formula Rate Proceedings- Pursuant to Section 206 of the Federal Power Act, there are several pending proceedings before the FERC concerning the justness and reasonableness of the Return on Equity (ROE) component of the ISO-New England, Inc. Participating Transmission Owners’ (PTOs) Regional Network Service and Local Network Service formula rates. In August 2013, FERC had found that the Transmission Owners existing ROE was unlawful, and set a new ROE. On April 14, 2017, the U.S. Court of Appeals for the D.C. Circuit (the Court) issued an opinion vacating and remanding FERC’s decision, finding that FERC had failed to articulate a satisfactory explanation for its orders. At this time, the ROE set in the vacated order will remain in place until further FERC action is taken. On November 21, 2019 the FERC issued an order in EL14-12, Midcontinent Independent System Operator ROE, in which FERC outlined a new methodology for calculating the ROE. The New England Transmission Owners (NETOs) thereafter filed a motion to reopen the record in their pending ROE dockets, which has been granted. This matter remains pending. The Company does not believe these proceedings will have a material adverse effect on its financial condition or results of operations.

On December 13, 2022, RENEW Northeast, Inc., a non-profit entity that advocates for the business interests of renewable power generators in New England filed a complaint with FERC against ISO-NE and the PTOs requesting a determination that certain open-access transmission tariff schedules are unjust and unreasonable to the extent they permit PTOs to directly assign to interconnection customers O&M costs associated with network upgrades. Fitchburg and Unitil Energy are PTOs, although Unitil Energy does not own transmission plant. The PTOs answered the complaint on January 23, 2023. This matter remains pending. The Company does not believe these proceedings will have a material adverse effect on its financial condition or results of operations.

Legal Proceedings

The Company is involved in legal and administrative proceedings and claims of various types, including those which arise in the ordinary course of business. The Company believes, based upon information furnished by counsel and others, that the ultimate resolution of these claims will not have a material effect on its financial position, operating results or cash flows.

Regulatory Liabilities (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 51.9	$ 47.9	$ 53.2
Less: Current Portion of Regulatory Liabilities	17.9	13.5	17.0
Regulatory Liabilities – noncurrent	34.0	34.4	36.2
Income Taxes
Regulatory Liabilities [Line Items]
Regulatory Liabilities	37.9	38.6	40.3
Rate Adjustment Mechanisms
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 14.0	$ 9.3	$ 12.9

DEBT AND FINANCING ARRANGEMENTS (Tables)

3 Months Ended

Mar. 31, 2024

Details on Long Term Debt

Details on long-term debt at March 31, 2024, March 31, 2023 and December 31, 2023 are shown below.


(millions)	March 31,				December 31,
	2024		2023		2023
Unitil Corporation:
3.70% Senior Notes, Due August 1, 2026	$	30.0	$	30.0	$	30.0
3.43% Senior Notes, Due December 18, 2029		30.0		30.0		30.0
Unitil Energy First Mortgage Bonds:
6.96% Senior Secured Notes, Due September 1, 2028		10.0		12.0		10.0
8.00% Senior Secured Notes, Due May 1, 2031		12.0		13.5		12.0
6.32% Senior Secured Notes, Due September 15, 2036		15.0		15.0		15.0
3.58% Senior Secured Notes, Due September 15, 2040		27.5		27.5		27.5
4.18% Senior Secured Notes, Due November 30, 2048		30.0		30.0		30.0
Fitchburg:
6.79% Senior Notes, Due October 15, 2025		—		2.0		—
3.52% Senior Notes, Due November 1, 2027		10.0		10.0		10.0
7.37% Senior Notes, Due January 15, 2029		6.0		7.2		7.2
5.90% Senior Notes, Due December 15, 2030		15.0		15.0		15.0
7.98% Senior Notes, Due June 1, 2031		14.0		14.0		14.0
5.70% Senior Notes, Due July 2, 2033		12.0		—		12.0
3.78% Senior Notes, Due September 15, 2040		27.5		27.5		27.5
4.32% Senior Notes, Due November 1, 2047		15.0		15.0		15.0
5.96% Senior Notes, Due July 2, 2053		13.0		—		13.0
Northern Utilities:
3.52% Senior Notes, Due November 1, 2027		20.0		20.0		20.0
7.72% Senior Notes, Due December 3, 2038		50.0		50.0		50.0
3.78% Senior Notes, Due September 15, 2040		40.0		40.0		40.0
4.42% Senior Notes, Due October 15, 2044		50.0		50.0		50.0
4.32% Senior Notes, Due November 1, 2047		30.0		30.0		30.0
4.04% Senior Notes, Due September 12, 2049		40.0		40.0		40.0
Granite State:
3.72% Senior Notes, Due November 1, 2027		15.0		15.0		15.0
Unitil Realty Corp.:
2.64% Senior Secured Notes, Due December 18, 2030		4.0		4.2		4.0
Total Long-Term Debt		516.0		497.9		517.2
Less: Unamortized Debt Issuance Costs		3.2		3.2		3.2
Total Long-Term Debt, net of Unamortized Debt Issuance Costs		512.8		494.7		514.0
Less: Current Portion		4.9		6.7		4.9
Total Long-term Debt, Less Current Portion	$	507.9	$	488.0	$	509.1

Fair Value of Long Term Debt


(millions)	March 31,				December 31,
	2024		2023		2023
Estimated Fair Value of Long-Term Debt	$	465.6	$	449.2	$	470.5

Borrowing Limits Amounts Outstanding and Amounts Available under Credit Facility

The following table details the borrowing limits, amounts outstanding and amounts available under the Credit Facility as of March 31, 2024, March 31, 2023 and December 31, 2023:


	Revolving Credit Facility (millions)
	March 31,				December 31,
	2024		2023		2023
Limit	$	200.0	$	200.0	$	200.0
Short-Term Borrowings Outstanding		169.9		140.2		162.0
Available	$	30.1	$	59.8	$	38.0

Classification of the Company Lease Obligations

The balance sheet classification of the Company’s lease obligations was as follows:


	March 31,				December 31,
Lease Obligations (millions)	2024		2023		2023
Operating Lease Obligations:
Other Current Liabilities (current portion)	$	1.8	$	1.8	$	1.9
Other Noncurrent Liabilities (long-term portion)		3.8		3.9		3.7
Total Operating Lease Obligations		5.6		5.7		5.6
Capital Lease Obligations:
Other Current Liabilities (current portion)		0.1		0.1		0.1
Other Noncurrent Liabilities (long-term portion)		0.3		0.3		0.4
Total Capital Lease Obligations		0.4		0.4		0.5
Total Lease Obligations	$	6.0	$	6.1	$	6.1

Future Operating Lease Payment Obligations and Future Minimum Lease Payments under Capital Leases

The following table is a schedule of future operating lease payment obligations and future minimum lease payments under capital leases as of March 31, 2024. The payments for operating leases consist of $1.8 million of current operating lease obligations, which are included in Other Current Liabilities and $3.8 million of noncurrent operating lease obligations, which are included in Other Noncurrent Liabilities, on the Company’s Consolidated Balance Sheets as of March 31, 2024. The payments for capital leases consist of $0.1 million of current capital lease obligations, which are included in Other Current Liabilities and $0.3 million of noncurrent capital lease obligations, which are included in Other Noncurrent Liabilities, on the Company’s Consolidated Balance Sheets as of March 31, 2024.


Lease Payments ($000’s)	Operating		Capital
Year Ending December 31,	Leases		Leases
Rest of 2024	$	1,607	$	122
2025		1,558		120
2026		1,270		107
2027		993		115
2028		420		19
2029 - 2033		223		—
Total Payments		6,071		483
Less: Interest		517		40
Amount of Lease Obligations Recorded on Consolidated Balance Sheets	$	5,554	$	443

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

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DEBT AND FINANCING ARRANGEMENTS - Estimated Fair Value Of Long Term Debt (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Debt Instrument [Line Items]
Estimated Fair Value of Long-Term Debt	$ 465.6	$ 470.5	$ 449.2

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair Value of Marketable Securities (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading Securities	$ 5.9	$ 6.0	$ 5.7
Deferred Compensation Plan [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading Securities	1.8	1.3	0.9
Fair Value, Inputs, Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading Securities	5.9	6.0	5.7
Fair Value, Inputs, Level 1 \| Deferred Compensation Plan [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading Securities	1.8	1.3	0.9
Fair Value, Inputs, Level 1 \| Equity Funds \| Deferred Compensation Plan [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading Securities	1.6	1.1	0.8
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Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading Securities	3.9	4.0	0.0
Fair Value, Inputs, Level 1 \| Fixed Income Funds [Member] \| Deferred Compensation Plan [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading Securities	0.1	0.1	0.0
Fair Value, Inputs, Level 1 \| Money Market Funds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading Securities	2.0	2.0	5.7
Fair Value, Inputs, Level 1 \| Money Market Funds \| Deferred Compensation Plan [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading Securities	$ 0.1	$ 0.1	$ 0.1

Pay vs Performance Disclosure - USD ($) $ in Millions	3 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Millions	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ 27.2	$ 24.1

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Reference 32: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483499/205-20-50-7

Reference 35: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-28

Reference 36: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1A

Reference 37: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1B

Reference 38: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-Publisher FASB
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Reference 39: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

+ Details

Regulatory Matters - Additional Information (Detail 1) $ in Millions											3 Months Ended		12 Months Ended
	Nov. 27, 2023 USD ($)	Nov. 01, 2023 USD ($)	Aug. 17, 2023 USD ($)	Jul. 27, 2023 USD ($)	Jul. 26, 2023 USD ($)	Dec. 30, 2022 USD ($)	Aug. 19, 2022 USD ($)	Aug. 24, 2021 USD ($)	Nov. 30, 2020 USD ($)	Jun. 25, 2019	Mar. 31, 2024 USD ($) MW	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Apr. 15, 2024 USD ($)	Dec. 31, 2023 USD ($)	Oct. 31, 2023 USD ($)	Aug. 30, 2023 MW	May 31, 2023 USD ($)	Nov. 30, 2022 USD ($)	Oct. 31, 2022 USD ($)	Oct. 07, 2022 USD ($)	May 25, 2022 MW	May 07, 2021 MW	Feb. 10, 2020 MW	May 31, 2019 MW	Jul. 31, 2018 MW MWh	Jun. 30, 2017 MW MWh
Regulatory Assets [Line Items]
Termination agreements											$ 1.1
Remuneration Percentage										2.75%	2.25%
Approved commitments for purchasing assets						$ 1.0
Fitchburg Gas And Electric Light Company [Member]
Regulatory Assets [Line Items]
Facility power capacity to be procured in the future \| MW																	400
Power generation capacity \| MWh																											9,450,000
Increase (decrease) in annual revenue	$ 3.5	$ 3.6			$ 3.1
Fitchburg Gas And Electric Light Company [Member] \| Offshore Energy [Member]
Regulatory Assets [Line Items]
Facility power capacity to be procured in the future \| MW											5,600						5,600
Remuneration Percentage										2.75%
Power generation facility \| MW																								400		400	1,600
Fitchburg Gas And Electric Light Company [Member] \| Qualified Clean Energy [Member]
Regulatory Assets [Line Items]
Power generation capacity \| MWh																										9,554,940
Fitchburg Gas And Electric Light Company [Member] \| Minimum [Member]
Regulatory Assets [Line Items]
Facility power capacity to be procured in the future \| MW											200
Fitchburg Gas And Electric Light Company [Member] \| Maximum [Member]
Regulatory Assets [Line Items]
Facility power capacity to be procured in the future \| MW											2,400
Fitchburg Gas Company [Member]
Regulatory Assets [Line Items]
Regulatory assets approved increase in revenue due to be recovered			$ 6.7													$ 6.4				$ 4.5
Increase (decrease) in annual revenue			4.2
Public utilities interim increase decrease amount			$ 10.9
Granite State [Member]
Regulatory Assets [Line Items]
Increase (decrease) in annual revenue				$ 1.0			$ 0.3	$ 0.1	$ 1.3
Spending cap									14.6
Fitchburg Grid Modernization [Member]
Regulatory Assets [Line Items]
Regulatory assets approved increase in revenue due to be recovered														$ 1.3				$ 1.0
Purchase commitments for data sharing platform investments									2.3
Amount of replacement investments approved by regulatory authority																			$ 11.2
Fitchburg Grid Modernization [Member] \| Track One [Member]
Regulatory Assets [Line Items]
Amount of capital expenditure approved by regulatory authority																					$ 9.3
Fitchburg Grid Modernization [Member] \| Track Two [Member]
Regulatory Assets [Line Items]
Amount of capital expenditure approved by regulatory authority									$ 1.5
Second Solicitation [Member] \| Fitchburg Gas And Electric Light Company [Member] \| Offshore Energy [Member]
Regulatory Assets [Line Items]
Power generation facility \| MW																							1,600		800
Third Solicitation [Member] \| Fitchburg Gas And Electric Light Company [Member] \| Commonwealth Wind [Member]
Regulatory Assets [Line Items]
Power generation facility \| MW																						1,200
Third Solicitation [Member] \| Fitchburg Gas And Electric Light Company [Member] \| Mayflower Wind energy [Member]
Regulatory Assets [Line Items]
Power generation facility \| MW																						400
Major Storm Cost Reserve Recovery [Member]
Regulatory Assets [Line Items]
Carrying costs													$ 0.2
Recover costs of repairing damage															$ 3.7
Storm Cost Deferral Petition [Member]
Regulatory Assets [Line Items]
Carrying costs												$ 1.4
Recover costs of repairing damage												$ 4.8
Marketing And Outreach [Member]
Regulatory Assets [Line Items]
Approved commitments for purchasing assets						0.2
Electric Vehicle Supply Equipment [Member]
Regulatory Assets [Line Items]
Approved commitments for purchasing assets						0.3
Public Infrastructure Offering [Member]
Regulatory Assets [Line Items]
Approved commitments for purchasing assets						$ 0.5

Retirement Benefit Obligations - Components of Retirement Plan Costs (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 497	$ 523
Interest Cost	1,886	1,870
Expected Return on Plan Assets	(2,649)	(2,672)
Prior Service Cost Amortization	81	89
Actuarial Loss Amortization	362	(0)
Sub-total	177	(190)
Amounts Capitalized and Deferred	108	498
Net Periodic Benefit Cost Recognized	$ 285	308
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 497	373
Interest Cost	817	725
Expected Return on Plan Assets	(969)	(852)
Prior Service Cost Amortization	0	198
Actuarial Loss Amortization	(219)	(366)
Sub-total	126	78
Amounts Capitalized and Deferred	124	221
Net Periodic Benefit Cost Recognized	$ 250	299
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 54	63
Interest Cost	181	188
Prior Service Cost Amortization	2	14
Actuarial Loss Amortization	(0)	0
Sub-total	237	265
Amounts Capitalized and Deferred	(73)	(82)
Net Periodic Benefit Cost Recognized	$ 164	$ 183
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)

CONSOLIDATED STATEMENTS OF CHANGES IN COMMON STOCK EQUITY (UNAUDITED) - USD ($) $ in Millions	Total	Common Equity	Retained Earnings
Beginning Balance at Dec. 31, 2022	$ 467.4	$ 334.9	$ 132.5
Net Income	24.1		24.1
Dividends on Common Shares	(6.5)		(6.5)
Stock Compensation Plans	0.9	0.9
Issuance of Common Shares	0.3	0.3
Ending Balance at Mar. 31, 2023	486.2	336.1	150.1
Beginning Balance at Dec. 31, 2023	489.1	337.6	151.5
Net Income	27.2		27.2
Dividends on Common Shares	(6.8)		(6.8)
Stock Compensation Plans	0.8	0.8
Issuance of Common Shares	0.3	0.3
Ending Balance at Mar. 31, 2024	$ 510.6	$ 338.7	$ 171.9

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

- Definition

Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

+ References + Details

Regulatory Matters - Additional Information (Detail) - USD ($) $ in Millions	May 01, 2024	Nov. 27, 2023	Nov. 01, 2023	Sep. 20, 2023	Aug. 17, 2023	Jul. 27, 2023	Jul. 26, 2023	May 31, 2023	Aug. 19, 2022	Jul. 28, 2022	Jul. 20, 2022	Jun. 08, 2022	May 12, 2022	May 03, 2022	Aug. 24, 2021	Nov. 30, 2020	Apr. 15, 2024	Oct. 31, 2023	Oct. 31, 2022
Regulatory Assets [Line Items]
Requested annual increase in rates	$ 2.4
Northern Utilities Inc
Regulatory Assets [Line Items]
Percentage of approved return on equity													9.20%
Percentage of approved return on equity, reflecting on equity													52.00%
Percentage of approved return on equity, reflecting on debt													48.00%
Approved annual increase in rates				$ 7.6										$ 6.3
Return on equity				9.35%
Equity ratio				52.01%
Weighted average cost of capital				7.22%
Public utilities approved increase amount of annual revenue to recover eligible capital investments								$ 1.2		$ 1.3
Northern Utilities Inc \| Settlement Agreement [Member]
Regulatory Assets [Line Items]
Approved annual increase in rates											$ 6.1
Northern Utilities Inc \| Arrearage Management Program [Member]
Regulatory Assets [Line Items]
Expenses associated with the program excluded from the revenue requirement as per order and adjusted increase amount will result in reasonable rates													$ 5.9
Northern Utilities Inc \| New Hampshire
Regulatory Assets [Line Items]
Percentage of approved return on equity											9.30%
Percentage of approved return on equity, reflecting on equity											52.00%
Percentage of approved return on equity, reflecting on debt											48.00%
Requested annual increase in rates												$ 1.6
Fitchburg Gas and Electric Light Company
Regulatory Assets [Line Items]
Increase (decrease) in annual revenue		$ 3.5	$ 3.6				$ 3.1
Transfer revenue amount					$ 2.7
Approved annual increase in rates					4.1
Fitchburg Gas and Electric Light Company \| July 1, 2024
Regulatory Assets [Line Items]
Approved annual increase in rates					6.8
Fitchburg Gas Company
Regulatory Assets [Line Items]
Increase (decrease) in annual revenue					4.2
Regulatory assets approved increase in revenue due to be recovered					$ 6.7													$ 6.4	$ 4.5
Granite State
Regulatory Assets [Line Items]
Increase (decrease) in annual revenue						$ 1.0			$ 0.3						$ 0.1	$ 1.3
Fitchburg - Grid Modernization
Regulatory Assets [Line Items]
Regulatory assets approved increase in revenue due to be recovered								$ 1.0									$ 1.3

EQUITY (Tables)

3 Months Ended

Mar. 31, 2024

Table Text Block Supplement [Abstract]

Restricted Stock Units Issued

The equity portion of Restricted Stock Units activity during the three months ended March 31, 2024 in conjunction with the Stock Plan is presented in the following table:


Restricted Stock Units (Equity Portion)
	Units		Weighted Average Stock Price
Restricted Stock Units as of December 31, 2023		33,375	$	42.73
Restricted Stock Units Granted		—	$	—
Dividend Equivalents Earned		278	$	50.96
Restricted Stock Units Settled		—	$	—
Restricted Stock Units as of March 31, 2024		33,653	$	42.80

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating Activities:
Net Income	$ 27.2	$ 24.1
Adjustments to Reconcile Net Income to Cash Provided by Operating Activities:
Depreciation and Amortization	18.0	16.7
Deferred Tax Provision	2.4	7.2
Changes in Working Capital Items:
Accounts Receivable	(8.9)	(18.4)
Accrued Revenue	(8.8)	1.2
Exchange Gas Receivable	7.2	13.3
Regulatory Liabilities	4.4	2.0
Accounts Payable	(9.8)	(22.3)
Other Changes in Working Capital Items	1.6	0.1
Deferred Regulatory and Other Charges	(9.0)	(10.9)
Other, net	2.3	2.3
Cash Provided by Operating Activities	26.6	15.3
Investing Activities:
Property, Plant and Equipment Additions	(20.2)	(22.2)
Cash Used in Investing Activities	(20.2)	(22.2)
Financing Activities:
Proceeds from Short-Term Debt, net	7.9	24.2
Repayment of Long-Term Debt	(1.3)	(1.2)
Net Decrease in Exchange Gas Financing	(6.7)	(12.3)
Increase in Capital Lease Obligations	0.0	0.2
Dividends Paid	(6.8)	(6.5)
Proceeds from Issuance of Common Stock	0.3	0.3
Cash (Used In) Provided by Financing Activities	(6.6)	4.7
Net Decrease in Cash and Cash Equivalents	(0.2)	(2.2)
Cash and Cash Equivalents at Beginning of Period	6.5	9.0
Cash and Cash Equivalents at End of Period	6.3	6.8
Supplemental Cash Flow Information:
Interest Paid	7.0	6.7
Income Taxes Paid	0.0	0.0
Payments on Capital Leases	0.0	0.1
Non-cash Investing Activity:
Capital Expenditures Included in Accounts Payable	5.3	5.6
Right-of-Use Assets Obtained in Exchange for Lease Obligations	$ 0.5	$ 1.4

DEBT AND FINANCING ARRANGEMENTS - Additional Information (Detail) - USD ($) shares in Millions, $ in Millions			3 Months Ended		12 Months Ended
	Jul. 06, 2023	Sep. 29, 2022	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Line of Credit Facility [Line Items]
Weighted average interest rate on short term borrowings			6.70%	5.90%	6.40%
Capital lease obligation, current			$ 0.1	$ 0.1	$ 0.1
Capital lease obligation, noncurrent			0.3	0.3	0.4
Accounts Payable			37.9	46.3	47.7
Total rental expense under operating leases			0.5	0.5
Net Utility Plant			1,429.8	1,341.3	1,420.9
Operating lease obligations			0.5	0.5
Other current operating lease obligation			1.8	1.8	1.9
Other noncurrent operating lease obligation			$ 3.8	$ 3.9	3.7
Operating lease, weighted average remaining lease term			3 years 8 months 12 days	3 years 9 months 18 days
Operating lease, weighted average discount rate percentage			4.60%	4.50%
Assets under Capital Leases [Member]
Line of Credit Facility [Line Items]
Net Utility Plant			$ 0.7	$ 0.9	0.7
Net Utility Plant, accumulated amortization			$ 0.2	0.4	0.2
Northern Utilities Inc
Line of Credit Facility [Line Items]
Total funded indebtedness as percentage of capitalization			65.00%
Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility			$ 200.0	$ 200.0	$ 200.0
Proceeds from lines of credit			85.9
Repayments of lines of credit			78.0
Accounts Payable			$ 1.4
Debt Instrument, Covenant Description			The affirmative and negative covenants under the Credit Facility shall apply to Unitil until the Credit Facility terminates and all amounts borrowed under Credit Facility are paid in full (or, with respect to letters of credit, they are cash-collateralized). The only financial covenant in the Credit Facility provides that Unitil’s Funded Debt to Capitalization (as each term is defined in the Credit Facility) cannot exceed 65% tested on a quarterly basis
Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility		$ 75.0
Credit Facility \| Third Amendment Credit Facility
Line of Credit Facility [Line Items]
Sublimit for the issuance of standby letters of credit		25.0
Revolving credit facility		$ 200.0
Credit Facility \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Subordinated Borrowing, Due Date	Jul. 02, 2053
cost of issue			$ 0.2
Debt Instrument, Interest Rate, Effective Percentage	5.96%
Debt Conversion, Converted Instrument, Warrants or Options Issued	13.0
Natural gas storage inventory			$ 3.3
Credit Facility \| Revolving Credit Facility \| Fitchburg [Member]
Line of Credit Facility [Line Items]
Debt Conversion, Converted Instrument, Shares Issued	12.0
Subordinated Borrowing, Due Date	Jul. 02, 2033
Debt Instrument, Interest Rate, Effective Percentage	5.70%
Credit Facility \| Revolving Credit Facility \| Third Amendment Credit Facility \| Secured Overnight Financing Rate [Member]
Line of Credit Facility [Line Items]
Credit facility, daily fluctuating rate of interest		0.10%
Credit Facility \| Revolving Credit Facility \| Third Amendment Credit Facility \| Secured Overnight Financing Rate [Member] \| Maximum [Member]
Line of Credit Facility [Line Items]
Debt instrument variable interest rate additional spread		1.375%
Credit Facility \| Revolving Credit Facility \| Third Amendment Credit Facility \| Secured Overnight Financing Rate [Member] \| Minimum [Member]
Line of Credit Facility [Line Items]
Debt instrument variable interest rate additional spread		1.125%

DIVIDENDS DECLARED PER SHARE

3 Months Ended

Mar. 31, 2024

DIVIDENDS DECLARED PER SHARE [Abstract]

DIVIDENDS DECLARED PER SHARE

Note 2 - Dividends Declared Per Share


Declaration Date	Date Paid (Payable)	Shareholder of Record Date	Dividend Amount
05/1/24	05/31/24	05/16/24	$	0.425
01/31/24	02/29/24	02/14/24	$	0.425
10/23/23	11/28/23	11/14/23	$	0.405
07/26/23	08/28/23	08/14/23	$	0.405
04/26/23	05/30/23	05/15/23	$	0.405
01/25/23	02/28/23	02/14/23	$	0.405

Environmental Matters

3 Months Ended

Mar. 31, 2024

Text Block [Abstract]

Environmental Matters

note 7 – eNVIRONMENTAL MATTERS

Unitil’s Environmental matters are described in Note 8 to the Financial Statements in Item 8 of Part II of Unitil Corporation’s Form 10-K for December 31, 2023 as filed with the Securities and Exchange Commission on february 13, 2024.

Environmental Matters

The Company’s past and present operations include activities that are generally subject to extensive and complex federal and state environmental laws and regulations. The Company is in material compliance with applicable environmental and safety laws and

regulations and, as of March 31, 2024, has not identified any material losses reasonably likely to be incurred in excess of recorded amounts. However, the Company cannot assure that significant costs and liabilities will not be incurred in the future. It is possible that other developments, such as increasingly stringent federal, state or local environmental laws and regulations could result in increased environmental compliance costs. Based on its current assessment of its environmental responsibilities, existing legal requirements and regulatory policies, the Company does not believe that these environmental costs will have a material adverse effect on the Company’s consolidated financial position or results of operations.

Northern Utilities Manufactured Gas Plant Sites - Northern Utilities has an extensive program to identify, investigate and remediate former manufactured gas plant (MGP) sites, which were operated from the mid-1800s through the mid-1900s. In New Hampshire, MGP sites were identified in Dover, Exeter, Portsmouth, Rochester and Somersworth. In Maine, Northern Utilities has documented the presence of MGP sites in Lewiston and Portland, and a former MGP disposal site in Scarborough.

Northern Utilities has worked with the New Hampshire Department of Environmental Services (NH DES) and Maine Department of Environmental Protection to address environmental concerns with these sites. Northern Utilities or others have completed remediation activities at all sites; however, on site monitoring continues at several sites which may result in future remedial actions as directed by the applicable regulatory agency.

The Company is awaiting a decision from the NH DES regarding three remediation alternatives, submitted to the NH DES in December 2022, regarding groundwater contaminants at the Rochester site. In anticipation of the probable NH DES approval of one of the remediation alternatives and subsequent request for project design, the Company has accrued $2.5 million for estimated costs to complete the remediation at the Rochester site, which is included in Environmental Obligations on the Company’s Consolidated Balance Sheets. The Company has determined that the high end of the range of reasonably possible remediation costs for the Rochester site could be $5.6 million based on remediation alternatives. Due to extended regulatory review time periods, Northern Utilities anticipates the commencement of remediation activities in 2025.

The NHPUC and MPUC have approved regulatory mechanisms for the recovery of MGP environmental costs. For Northern Utilities’ New Hampshire division, the NHPUC has approved the recovery of MGP environmental costs over succeeding seven-year periods. For Northern Utilities’ Maine division, the MPUC has authorized the recovery of environmental remediation costs over succeeding five-year periods.

The Environmental Obligations table includes amounts accrued for Northern Utilities related to estimated future cleanup costs associated with Northern Utilities’ environmental remediation obligations for former MGP sites. Corresponding Regulatory Assets were recorded to reflect that the future recovery of these environmental remediation costs is expected based on regulatory precedent and established practices.

Fitchburg’s Manufactured Gas Plant Site - Fitchburg has worked with the Massachusetts Department of Environmental Protection (MA DEP) to address environmental concerns with the former MGP site at Sawyer Passway, and has substantially completed remediation activities, though on site monitoring and any related remediation continues. In April 2020, Fitchburg received notification from the Massachusetts Department of Transportation (MA DOT) that a portion of the site may be incorporated into the proposed Twin City Rail Trail with an anticipated commencement date in 2025. Depending upon the final agreement between Fitchburg and MA DOT, additional minor costs are expected prior to completion.

The Company is awaiting a decision regarding an Immediate Response Action (IRA) plan with three remediation alternatives, submitted to the MA DEP in October 2023, regarding contaminants in the sediment and riverbank of an abutting watercourse, and observed river seep. In anticipation of the DEP accepting one of the remediation alternatives, Fitchburg has accrued $40,000 for estimated costs to complete the remediation at the Sawyer Passway site, which is included in Environmental Obligations on the Company’s Consolidated Balance Sheets. The Company has determined that the high end of the range of reasonably possible remediation costs for the Sawyer Passway site could be $3.5 million based on remediation alternatives. Fitchburg anticipates the commencement of remediation activities by the end of 2024.

Fitchburg recovers the environmental response costs incurred at this former MGP site in gas rates pursuant to the terms of a cost recovery agreement approved by the MDPU. Pursuant to this agreement, Fitchburg is authorized to amortize and recover environmental response costs from gas customers over succeeding seven-year periods.

Unitil Energy - Kensington Distribution Operations Center - Unitil Energy conducted a Phase I and II environmental site assessment (ESA) in the second quarter of 2021 at its former distribution operations center in Kensington, NH. The Company is awaiting a decision on a report, submitted to the NH DES in June 2023, as to whether there is a need to conduct further investigation or remedial actions regarding the impacts of soil and groundwater contaminants identified in the ESA .

Unitil Energy anticipates the commencement of remediation activities in 2025. The Company does not believe this investigation will have a material adverse effect on its financial condition, results of operations or cash flows.

The following table sets forth a summary of changes in the Company’s liability for Environmental Obligations for the three months ended March 31, 2024 and 2023.


Environmental Obligations (millions)
	March 31,
	2024		2023
Total Balance at Beginning of Period	$	4.6	$	4.4
Additions		0.3		0.5
Less: Payments / Reductions		0.1		0.2
Total Balance at End of Period		4.8		4.7
Less: Current Portion		0.7		0.6
Noncurrent Balance at End of Period	$	4.1	$	4.1

- Definition

The entire disclosure for environmental loss contingencies, such as presence of hazardous waste, relevant information from reports issued by regulators, and estimated costs to achieve compliance with regulatory requirements. This element may be used for all of an entity's disclosures about environmental loss contingencies.

+ References

Reference 1: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481931/410-30-50-10

Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Subparagraph (d)(3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481931/410-30-50-10

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481899/410-30-55-11

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 16
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481899/410-30-55-16

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//410-30/tableOfContent

Reference 6: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481931/410-30-50-10

Reference 7: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481931/410-30-50-10

Reference 8: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481931/410-30-50-10

Reference 9: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Subparagraph (d)(4)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481931/410-30-50-10

Reference 10: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Subparagraph (d)(5)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481931/410-30-50-10

Reference 11: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481931/410-30-50-11

Reference 12: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481931/410-30-50-14

Reference 13: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481931/410-30-50-17

Reference 14: http://www.xbrl.org/2003/role/exampleRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481899/410-30-55-17

+ Details

DEBT AND FINANCING ARRANGEMENTS - Classification Of The Company Lease Obligations (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Operating Lease Obligations:
Other Current Liabilities (current portion)	$ 1.8	$ 1.9	$ 1.8
Other Noncurrent Liabilities (long-term portion)	3.8	3.7	3.9
Total Operating Lease Obligations	5.6	5.6	5.7
Capital Lease Obligations:
Other Current Liabilities (current portion)	0.1	0.1	0.1
Other Noncurrent Liabilities (long-term portion)	0.3	0.4	0.3
Total Capital Lease Obligations	0.4	0.5	0.4
Total Lease Obligations	6.0	$ 6.1	$ 6.1
Lease Obligations [Member]
Operating Lease Obligations:
Total Operating Lease Obligations	$ 5,554.0

DEBT AND FINANCING ARRANGEMENTS - Future Operating Lease Payment Obligations And Future Minimum Lease Payments Under Capital Leases (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Operating leases
Rest of 2024	$ 1,607.0
2025	1,558.0
2026	1,270.0
2027	993.0
2028	420.0
2029-2033	223.0
Total Payments	6,071.0
Less: Interest	517.0
Amount of Lease Obligations Recorded on Consolidated Balance Sheets	5.6	$ 5.6	$ 5.7
Capital leases
Rest of 2024	122.0
2025	120.0
2026	107.0
2027	115.0
2028	19.0
2029-2033	0.0
Total Payments	483.0
Less: Interest	40.0
Lease Obligations [Member]
Operating leases
Amount of Lease Obligations Recorded on Consolidated Balance Sheets	5,554.0
Capital leases
Amount of Lease Obligations Recorded on Consolidated Balance Sheets	$ 443.0

Key Weighted Average Assumptions Used in Determining Benefit Plan Costs and Obligations (Detail) - Benefit Plan Costs [Member]	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	5.00%	5.25%
Rate of Compensation Increase	3.00%	3.00%
Expected Long-term rate of return on plan assets	7.50%	7.50%

Retirement Benefit obligations (Tables)

3 Months Ended

Mar. 31, 2024

Key Weighted Average Assumptions Used in Determining Benefit Plan Costs and Obligations

The following table includes the key weighted average assumptions used in determining the Company’s benefit plan costs and obligations:


Used to Determine Plan Costs	2024			2023
Discount Rate		5.00	%		5.25	%
Rate of Compensation Increase		3.00	%		3.00	%
Expected Long-term rate of return on plan assets		7.50	%		7.50	%

Components of Retirement Plan Costs

The following tables provide the components of the Company’s Retirement plan costs ($000’s):


	Pension Plan						PBOP Plan						SERP
For the Three Months Ended March 31,	2024			2023			2024			2023			2024			2023
Service Cost	$	497		$	523		$	497		$	373		$	54		$	63
Interest Cost		1,886			1,870			817			725			181			188
Expected Return on Plan Assets		(2,649	)		(2,672	)		(969	)		(852	)		—			—
Prior Service Cost Amortization		81			89			—			198			2			14
Actuarial Loss Amortization		362			—			(219	)		(366	)		—			0
Sub-total		177			(190	)		126			78			237			265
Amounts Capitalized and Deferred		108			498			124			221			(73	)		(82	)
Net Periodic Benefit Cost Recognized	$	285		$	308		$	250		$	299		$	164		$	183

Environmental Matters - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 31, 2023	Mar. 31, 2024	Dec. 31, 2022
Site Contingency [Line Items]
Amortization period for environmental costs		5 years
remediation costs			$ 5.6
Environmental Restoration Costs
Site Contingency [Line Items]
Estimated Costs Accrued For Remediation			$ 2.5
Fitchburg Manufactured Gas Plant Site [Member]
Site Contingency [Line Items]
Estimated Costs Accrued For Remediation	$ 40,000.0
remediation costs	$ 3.5

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

DIVIDENDS DECLARED PER SHARE (Tables)

3 Months Ended

Mar. 31, 2024

DIVIDENDS DECLARED PER SHARE [Abstract]

Schedule of Dividends Declared


Declaration Date	Date Paid (Payable)	Shareholder of Record Date	Dividend Amount
05/1/24	05/31/24	05/16/24	$	0.425
01/31/24	02/29/24	02/14/24	$	0.425
10/23/23	11/28/23	11/14/23	$	0.405
07/26/23	08/28/23	08/14/23	$	0.405
04/26/23	05/30/23	05/15/23	$	0.405
01/25/23	02/28/23	02/14/23	$	0.405

DEBT AND FINANCING ARRANGEMENTS - Borrowing Limits Amounts Outstanding And Amounts Available Under Revolving Credit Facility (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Debt Instrument [Line Items]
Short-Term Borrowings Outstanding	$ 169.9	$ 162.0	$ 140.2
Revolving Credit Facility
Debt Instrument [Line Items]
Revolving Credit Facility, Limit	200.0	200.0	200.0
Short-Term Borrowings Outstanding	169.9	162.0	140.2
Available Revolving Credit Facility	$ 30.1	$ 38.0	$ 59.8

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

INCOME TAXES

3 Months Ended

Mar. 31, 2024

Income Tax Disclosure [Abstract]

Income Taxes

Note 8: INCOME TAXES

The differences between the Company’s provisions for Income Taxes and the provisions calculated at the statutory federal tax rate, expressed in percentages, are shown in the following table:


	For the Three Months Ended March 31,
	2024			2023
Statutory Federal Income Tax Rate		21	%		21	%
Income Tax Effects of:
State Income Taxes, net		6			6
Utility Plant Differences		(1	)		(1	)
Effective Income Tax Rate		26	%		26	%

Under the Company’s Tax Sharing Agreement (the Agreement) which was approved upon the formation of Unitil as a public utility holding company, the Company files consolidated Federal and State tax returns and Unitil Corporation and each of its utility operating subsidiaries recognize the results of their operations in its tax returns as if it were a stand-alone taxpayer. The Agreement provides that the Company will account for income taxes in compliance with U.S. GAAP and regulatory accounting principles. The Company has evaluated its tax positions at March 31, 2024 in accordance with the FASB Codification, and has concluded that no adjustment for recognition, de-recognition, settlement or foreseeable future events to any tax liabilities or assets as defined by the FASB Codification is required. The Company remains subject to examination by Maine, Massachusetts, and New Hampshire tax authorities for the tax periods ended December 31, 2022; December 31, 2021; and December 31, 2020.

Income tax filings for the year ended December 31, 2022 have been filed with the IRS, Massachusetts Department of Revenue, the Maine Revenue Service, and the New Hampshire Department of Revenue Administration. In the Company’s federal tax returns for the year ended December 31, 2022 which were filed with the IRS in October 2023, the Company utilized federal Net Operating Loss Carryforward (NOLC) assets of $1.4 million and $0.2 million of federal tax credit carryforward. As of December 31, 2023, the Company recognized the utilization of approximately $4.4 million of the NOLC asset and $1.7 million of federal tax credits available to offset current taxes payable. In addition, at December 31, 2023, the Company had $1.3 million of cumulative state tax credit carryforwards to offset future income taxes payable. If unused, the Company’s state tax credit carryforwards will begin to expire in 2027.

On April 14, 2023, the IRS issued Revenue Procedure 2023-15 that provides a safe harbor method of accounting that taxpayers may use to determine whether to deduct or capitalize expenditures to repair, maintain, replace, or improve natural gas transmission and distribution property. Under the revenue procedure, the method of accounting will depend on the property’s classification as linear transmission property, linear distribution property, or non-linear property. The revenue procedure may be adopted in tax years ending after May 1, 2023. The Company is evaluating the revenue procedure and the effect adopting the safe harbor would have on its property that is subject to this guidance.

In August 2022, the Inflation Reduction Act of 2022 (IRA) was signed into law. The IRA included new taxes on corporations, including the Corporate Alternative Minimum Tax (AMT) and the Excise Tax on Repurchase of Corporate Stock. The AMT is equal to 15% of a corporation’s adjusted financial statement income (AFSI). The AMT applies to companies that have a 3 year average AFSI of greater than $1

billion. The IRA also extended and modified certain renewable energy related credits. The Company has evaluated the provisions and determined that they do not have a material effect on the Company’s financial statements as of March 31, 2024.

In December 2017, the Tax Cuts and Jobs Act (TCJA), which included a reduction to the corporate federal income tax rate to 21% effective January 1, 2018, was signed into law. In accordance with FASB Codification Topic 740, the Company revalued its Accumulated Deferred Income Taxes (ADIT) at the new 21% tax rate at which the ADIT will be reversed in future periods. Based on communications received by the Company from its state regulators in rate cases and other regulatory proceedings in the first quarter of 2018 and as prescribed in the TCJA, FERC guidance and IRS normalization rules, the benefit of protected excess ADIT amounts will be subject to flow back to customers in future utility rates according to the Average Rate Assumption Method (ARAM). ARAM reconciles excess ADIT at the reversal rate of the underlying book/tax temporary timing differences. The Company estimates the ARAM flow back period for protected and unprotected excess ADIT to be between fifteen and twenty years over the remaining life of the related utility plant. Subject to regulatory approval, the Company expects to flow back to customers a net $47.1 million of protected excess ADIT created as a result of the lowering of the statutory tax rate by the TCJA over periods estimated to be fifteen to twenty years. As of March 31, 2024, the Company flowed back $10.1 million to customers in its Massachusetts, Maine, New Hampshire, and federal jurisdictions.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-21

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482526/740-270-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Regulatory Assets (Detail) - USD ($)
$ in Millions

Mar. 31, 2024

Dec. 31, 2023

Mar. 31, 2023

Regulatory Assets [Line Items]

Regulatory Assets

$ 117.2

$ 109.6

$ 118.0

Less: Current Portion of Regulatory Assets

^[1]

65.1

56.5

66.4

Regulatory Assets – noncurrent

52.1

53.1

51.6

Environmental Matters

Regulatory Assets [Line Items]

Regulatory Assets

6.2

6.1

6.2

Other Deferred Charges

Regulatory Assets [Line Items]

Regulatory Assets

12.6

11.0

11.2

Retirement Benefits

Regulatory Assets [Line Items]

Regulatory Assets

27.4

29.8

28.0

Deferred Storm Charges

Regulatory Assets [Line Items]

Regulatory Assets

7.8

9.2

7.7

Income Taxes

Regulatory Assets [Line Items]

Regulatory Assets

0.9

1.1

1.6

Energy Supply and Other Rate Adjustment Mechanisms

Regulatory Assets [Line Items]

Regulatory Assets

$ 62.3

$ 52.4

$ 63.3

[1]	Reflects amounts included in the Accrued Revenue on the Company’s Consolidated Balance Sheets.

DEBT AND FINANCING ARRANGEMENTS

3 Months Ended

Mar. 31, 2024

Debt And Financing Arrangements

Note 4 - Debt AND FINANCING ARRANGEMENTS

Details on long-term debt at March 31, 2024, March 31, 2023 and December 31, 2023 are shown below.


(millions)	March 31,				December 31,
	2024		2023		2023
Unitil Corporation:
3.70% Senior Notes, Due August 1, 2026	$	30.0	$	30.0	$	30.0
3.43% Senior Notes, Due December 18, 2029		30.0		30.0		30.0
Unitil Energy First Mortgage Bonds:
6.96% Senior Secured Notes, Due September 1, 2028		10.0		12.0		10.0
8.00% Senior Secured Notes, Due May 1, 2031		12.0		13.5		12.0
6.32% Senior Secured Notes, Due September 15, 2036		15.0		15.0		15.0
3.58% Senior Secured Notes, Due September 15, 2040		27.5		27.5		27.5
4.18% Senior Secured Notes, Due November 30, 2048		30.0		30.0		30.0
Fitchburg:
6.79% Senior Notes, Due October 15, 2025		—		2.0		—
3.52% Senior Notes, Due November 1, 2027		10.0		10.0		10.0
7.37% Senior Notes, Due January 15, 2029		6.0		7.2		7.2
5.90% Senior Notes, Due December 15, 2030		15.0		15.0		15.0
7.98% Senior Notes, Due June 1, 2031		14.0		14.0		14.0
5.70% Senior Notes, Due July 2, 2033		12.0		—		12.0
3.78% Senior Notes, Due September 15, 2040		27.5		27.5		27.5
4.32% Senior Notes, Due November 1, 2047		15.0		15.0		15.0
5.96% Senior Notes, Due July 2, 2053		13.0		—		13.0
Northern Utilities:
3.52% Senior Notes, Due November 1, 2027		20.0		20.0		20.0
7.72% Senior Notes, Due December 3, 2038		50.0		50.0		50.0
3.78% Senior Notes, Due September 15, 2040		40.0		40.0		40.0
4.42% Senior Notes, Due October 15, 2044		50.0		50.0		50.0
4.32% Senior Notes, Due November 1, 2047		30.0		30.0		30.0
4.04% Senior Notes, Due September 12, 2049		40.0		40.0		40.0
Granite State:
3.72% Senior Notes, Due November 1, 2027		15.0		15.0		15.0
Unitil Realty Corp.:
2.64% Senior Secured Notes, Due December 18, 2030		4.0		4.2		4.0
Total Long-Term Debt		516.0		497.9		517.2
Less: Unamortized Debt Issuance Costs		3.2		3.2		3.2
Total Long-Term Debt, net of Unamortized Debt Issuance Costs		512.8		494.7		514.0
Less: Current Portion		4.9		6.7		4.9
Total Long-term Debt, Less Current Portion	$	507.9	$	488.0	$	509.1

Fair Value of Long-Term Debt - Currently, the Company believes there is no active market in the Company’s debt securities, which have all been sold through private placements. If there were an active market for the Company’s debt securities, the fair value of the Company’s long-term debt would be estimated based on the quoted market prices for the same or similar issues, or on the current rates offered to the Company for debt of the same remaining maturities. The fair value of the Company’s long-term debt is estimated using Level 2 inputs (valuations based on quoted prices available in active markets for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, inputs other than quoted prices that are directly observable, and inputs derived principally from market data). In estimating the fair value of the Company’s long-term debt, the assumed market yield reflects the Moody’s Baa Utility Bond Average Yield. Costs, including prepayment costs, associated with the early settlement of long-term debt are not taken into consideration in determining fair value.


(millions)	March 31,				December 31,
	2024		2023		2023
Estimated Fair Value of Long-Term Debt	$	465.6	$	449.2	$	470.5

On September 29, 2022, the Company entered into a Third Amended and Restated Credit Agreement with a syndicate of lenders (collectively, the "Credit Facility”), which amended and restated in its entirety the prior credit facility. Unitil may borrow under the

Credit Facility until September 29, 2027, subject to two one-year extensions under certain circumstances. The Credit Facility terminates and all amounts outstanding thereunder are due and payable on September 29, 2027, subject to the potential extension discussed in the prior sentence.

The Credit Facility has a borrowing limit of $200 million, which includes a $25 million sublimit for the issuance of standby letters of credit. Unitil may increase the borrowing limit under the Credit Facility by up to $75 million under certain circumstances. The Credit Facility generally provides Unitil with the ability to elect that borrowings under the Credit Facility bear interest under several options, including a daily fluctuating rate equal to (a) the forward-looking secured overnight financing rate (as administered by the Federal Reserve Bank of New York) term rate with a term equivalent to one month beginning on that date, plus (b) 0.1000%, plus (c) a margin of 1.125% to 1.375% (based on Unitil’s credit rating).

The Company utilizes the Credit Facility for cash management purposes related to its short-term operating activities. Total gross borrowings were $85.9 million for the three months ended March 31, 2024. Total gross repayments were $78.0 million for the three months ended March 31, 2024. The following table details the borrowing limits, amounts outstanding and amounts available under the Credit Facility as of March 31, 2024, March 31, 2023 and December 31, 2023:


	Revolving Credit Facility (millions)
	March 31,				December 31,
	2024		2023		2023
Limit	$	200.0	$	200.0	$	200.0
Short-Term Borrowings Outstanding		169.9		140.2		162.0
Available	$	30.1	$	59.8	$	38.0

The Credit Facility contains customary terms and conditions for credit facilities of this type, including affirmative and negative covenants. There are restrictions on, among other things, Unitil’s and its subsidiaries’ ability to incur liens or incur indebtedness, and restrictions on Unitil’s ability to merge or consolidate with another entity or change its line of business. The affirmative and negative covenants under the Credit Facility shall apply to Unitil until the Credit Facility terminates and all amounts borrowed under Credit Facility are paid in full (or, with respect to letters of credit, they are cash-collateralized). The only financial covenant in the Credit Facility provides that Unitil’s Funded Debt to Capitalization (as each term is defined in the Credit Facility) cannot exceed 65% tested on a quarterly basis. At March 31, 2024, March 31, 2023 and December 31, 2023, the Company was in compliance with the covenants contained in the Credit Facility in effect on those dates.

The average interest rates on all short-term borrowings and intercompany money pool transactions were 6.7% and 5.9% for the three months ended March 31, 2024 and March 31, 2023, respectively. The average interest rate on all short-term borrowings for the twelve months ended December 31, 2023 was 6.4%.

On July 6, 2023, Fitchburg issued $12.0 million of Notes due July 2, 2033 at 5.70% and $13.0 million of Notes due July 2, 2053 at 5.96%. Fitchburg used the net proceeds from these offerings to refinance existing debt and for general corporate purposes. Approximately $0.2 million of costs associated with this issuance were recorded as a reduction of Long-Term Debt for presentation purposes on the Consolidated Balance Sheet in the third quarter of 2023.

Northern Utilities enters into asset management agreements under which Northern Utilities releases certain gas pipeline and storage assets, sells to an asset manager and subsequently repurchases the gas over the course of the gas heating season at the same price at which it sold the gas to the asset manager. There was $3.3 million of natural gas storage inventory and corresponding obligations at March 31, 2024 related to these asset management agreements. The amount of natural gas inventory released in March 2024, which was payable in April 2024, was $1.4 million and was recorded in Accounts Payable at March 31, 2024.

Guarantees

The Company provides limited guarantees on certain energy and gas storage management contracts entered into by the distribution utilities. The Company’s policy is to limit the duration of these guarantees. As of March 31, 2024, there were no guarantees outstanding.

Leases

Unitil’s subsidiaries lease some of their vehicles, machinery and office equipment under both capital and operating lease arrangements.

Total rental expense under operating leases charged to operations for the three months ended March 31, 2024 and March 31, 2023 amounted to $0.5 million and $0.5 million, respectively.

The balance sheet classification of the Company’s lease obligations was as follows:


	March 31,				December 31,
Lease Obligations (millions)	2024		2023		2023
Operating Lease Obligations:
Other Current Liabilities (current portion)	$	1.8	$	1.8	$	1.9
Other Noncurrent Liabilities (long-term portion)		3.8		3.9		3.7
Total Operating Lease Obligations		5.6		5.7		5.6
Capital Lease Obligations:
Other Current Liabilities (current portion)		0.1		0.1		0.1
Other Noncurrent Liabilities (long-term portion)		0.3		0.3		0.4
Total Capital Lease Obligations		0.4		0.4		0.5
Total Lease Obligations	$	6.0	$	6.1	$	6.1

Cash paid for amounts included in the measurement of operating lease obligations for the three months ended March 31, 2024 and March 31, 2023 was $0.5 million and $0.5 million and was included in Cash Provided by Operating Activities on the Consolidated Statements of Cash Flows.

Assets under capital leases amounted to approximately $0.7 million, $0.9 million and $0.7 million as of March 31, 2024, March 31, 2023 and December 31, 2023, respectively, less accumulated amortization of $0.2 million, $0.4 million and $0.2 million, respectively and are included in Net Utility Plant on the Company’s Consolidated Balance Sheets.


Lease Payments ($000’s)	Operating		Capital
Year Ending December 31,	Leases		Leases
Rest of 2024	$	1,607	$	122
2025		1,558		120
2026		1,270		107
2027		993		115
2028		420		19
2029 - 2033		223		—
Total Payments		6,071		483
Less: Interest		517		40
Amount of Lease Obligations Recorded on Consolidated Balance Sheets	$	5,554	$	443

Operating lease obligations are based on the net present value of the remaining lease payments over the remaining lease term. In determining the present value of lease payments, the Company used the interest rate stated in each lease agreement. As of March 31, 2024, the weighted average remaining lease term is 3.7 years and the weighted average operating discount rate used to determine the operating lease obligations was 4.6%. As of March 31, 2023, the weighted average remaining lease term was 3.8 years and the weighted average operating discount rate used to determine the operating lease obligations was 4.5%.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 470
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//470/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1E

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Section 50
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-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

+ Details

Cover Page - shares	3 Months Ended
Cover Page - shares	Mar. 31, 2024	May 03, 2024
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Amendment Flag	false
Document Period End Date	Mar. 31, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Registrant Name	UNITIL CORPORATION
Entity Central Index Key	0000755001
Entity File Number	1-8858
Entity Tax Identification Number	02-0381573
Entity Incorporation, State or Country Code	NH
Entity Shell Company	false
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Emerging Growth Company	false
Entity Address, Address Line One	6 Liberty Lane West
Entity Address, City or Town	Hampton
Entity Address, State or Province	NH
Entity Address, Postal Zip Code	03842-1720
City Area Code	603
Local Phone Number	772-0775
Title of 12(b) Security	Common Stock
Trading Symbol	UTL
Security Exchange Name	NYSE
Entity Common Stock, Shares Outstanding		16,168,480

INCOME TAXES - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Aug. 31, 2022	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2020	Dec. 31, 2017
Income Taxes [Line Items]
Corporate federal income tax		21.00%	21.00%
Regulatory liability, expected flow back to customers						$ 47.1
Regulatory liability, expected pass back to ratepayers				$ 1.3
Net Operating Loss Carryforwards Utilized For Income Taxes					$ 1.4
Current Federal Tax Expense (Benefit)					$ 0.2
Deferred tax assets, operating loss carryforwards, federal				4.4
Federal Tax Credits to Offset Current Taxes				$ 1.7
Percentage of alternate minimum tax	15.00%
Adjustment financial statement income	$ 1,000.0
Number of years used for calculating adjusted financial statement income	3 years
Gas Ratepayers \| Massachusetts And Maine [Member]
Income Taxes [Line Items]
Regulatory liability, expected flow back to customers		$ 10.1
Tax Year 2018
Income Taxes [Line Items]
Corporate federal income tax						21.00%	21.00%