UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-Q

☒ QUARTERLY REPORT UNDER SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended September 30, 2026

or

☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from to

Commission File Number 1-8858

UNITIL CORPORATION

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (603) 772-0775

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ☒

Indicate the number of shares outstanding of each of the issuer’s classes of common stock, as of the latest practicable date.

UNITIL CORPORATION AND SUBSIDIARY COMPANIES

FORM 10-Q

For the Quarter Ended September 30, 2026

Table of Contents

In this Quarterly Report on Form 10-Q, the “Company,” “Unitil,” “we,” “us,” “our” and similar terms refer to Unitil Corporation and its subsidiaries, unless the context requires otherwise.

Cautionary Statement

This report and the documents incorporated by reference into this report contain statements that constitute “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended (the Securities Act), Section 21E of the Securities Exchange Act of 1934, as amended (the Exchange Act), and the Private Securities Litigation Reform Act of 1995. All statements, other than statements of historical fact, included or incorporated by reference into this report, including, without limitation, statements regarding the financial position, business strategy and other plans and objectives for the future operations of the Company, are forward-looking statements.

These statements include declarations regarding the Company’s beliefs and current expectations. In some cases, forward-looking statements can be identified by terminology such as “may,” “will,” “should,” “expects,” “plans,” “anticipates,” “believes,” “estimates,” “predicts,” “potential” or “continue” or the negative of such terms or other comparable terminology. These forward-looking statements are subject to inherent risks and uncertainties in predicting future results and conditions that could cause the actual results to differ materially from those projected in these forward-looking statements. Some, but not all, of the risks and uncertainties include those described in Part II, Item 1A (Risk Factors) and the following:

Many of these risks are beyond the Company’s control. Any forward-looking statements speak only as of the date of this report, and the Company undertakes no obligation to update any forward-looking statements to reflect events or circumstances after the date on which such statements are made or to reflect the occurrence of unanticipated events, except as required by law. New factors emerge from time to time, and it is not possible for the Company to predict all such factors, nor can the Company assess the effect of any such factor on its business or the extent to which any factor, or combination of factors, may cause results to differ materially from those contained in any forward-looking statements.

PART I. FINANCIAL INFORMATION

Item 1. Financial Statements

See the information beginning on page 17 of this Quarterly Report on Form 10-Q.

Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations

See Part II, Item 7. “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in Unitil Corporation’s 2025 Annual Report on Form 10-K for additional information.

OVERVIEW

Unitil Corporation (Unitil or the Company) is a public utility holding company headquartered in Hampton, New Hampshire. 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.

Unitil’s principal business is the local distribution of electricity, natural gas and water throughout its service territory in the states of New Hampshire, Massachusetts and Maine. Unitil is the parent company of five wholly owned energy distribution utilities and two wholly owned water distribution utilities:

Unitil Energy, Fitchburg, Northern Utilities, Bangor and Maine Natural are collectively referred to as the “energy distribution utilities.” Together, the energy distribution utilities serve approximately 110,100 electric customers and 105,000 gas customers.

AWC-NH and Abenaki are collectively referred to as the “water distribution utilities.” Together, the water distribution utilities serve approximately 10,700 water customers.

Unitil also is the parent company of Granite State Gas Transmission, Inc. (Granite State), 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 major gas pipelines and access to domestic gas supplies in the south and Canadian gas supplies in the north.

At September 30, 2026, Unitil had an investment in Net Utility Plant of $2.0 billion. Earnings from Unitil’s utility operations are derived primarily from the return on investment in the utility assets of the five energy distribution utilities, the two water distribution utilities and Granite State.

The Company’s other subsidiaries include Unitil Service Corp., which provides, at cost, a variety of administrative and professional services to Unitil’s affiliated companies; Unitil Realty Corp., which owns and manages Unitil’s corporate office building and property located in Hampton, New Hampshire and owns land in Kingston, New Hampshire, on which Unitil Energy’s solar facility is located; Unitil Power Corp., which formerly functioned as the full requirements wholesale power supply provider for Unitil Energy; Unitil Resources, Inc., a non-regulated subsidiary, which currently does not have any activity; and Unitil Water Corp., which currently does not have any activity. Unitil’s consolidated net income includes the earnings of the holding company and these subsidiaries.

REGULATION

Unitil is subject to comprehensive regulation by federal and state regulatory authorities. Unitil and its energy distribution subsidiaries are subject to regulation as a holding company system by the FERC under the Energy Policy Act of 2005 regarding certain bookkeeping, accounting and reporting requirements. Unitil’s utility operations related to wholesale and interstate energy business activities also are regulated by the FERC. Unitil’s distribution utilities are subject to regulation by the applicable state public utility commissions with regard to their rates, issuance of securities and other accounting and operational matters: Unitil Energy is subject to regulation by the New Hampshire Public Utilities Commission (NHPUC); Fitchburg is subject to regulation by the Massachusetts Department of Public Utilities (MDPU); Northern Utilities is regulated by the NHPUC and the Maine Public Utilities Commission (MPUC); Bangor and Maine Natural are subject to regulation by the MPUC; and AWC-NH and Abenaki are subject to regulation by the NHPUC. Granite State, Unitil’s interstate gas transmission pipeline, is subject to regulation by FERC regarding its rates and operations. Because Unitil’s primary operations are subject to rate regulation, the regulatory treatment of various matters could significantly affect the Company’s operations and financial position.

Primarily all of Unitil's distribution subsidiaries deliver electricity, natural gas and/or water to all customers at rates established under cost of service regulation. Under this regulatory structure, Unitil’s distribution utilities are provided the opportunity to recover the cost of providing distribution service to their customers based on a test year, and to earn a reasonable return on their capital investment on

utility assets. In addition, the Company’s distribution utilities and its natural gas transmission pipeline company may recover certain base rate costs, including capital project spending and enhanced reliability and vegetation management programs, through annual step adjustments and cost tracking rate mechanisms. Bangor and Maine Natural’s Augusta Service Area deliver natural gas to their customers at rates established under alternative rate plans, which provide multi-year rate changes designed to approximate market-based rates.

The Company's electric and gas sales in Massachusetts and New Hampshire are now largely decoupled. Revenue decoupling eliminates the dependency of distribution revenue on the volume of electricity or gas sold. 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 MDPU and NHPUC.

RESULTS OF OPERATIONS

The following section of MD&A compares the results of operations for each of the two fiscal periods ended September 30, 2026 and September 30, 2025 and should be read in conjunction with the accompanying unaudited Consolidated Financial Statements and the accompanying Notes to unaudited Consolidated Financial Statements included in Part I, Item 1 of this report, which are prepared in accordance with accounting principles generally accepted in the United States of America (GAAP).

The Company’s results of operations historically have reflected the seasonal nature of the natural gas business. Annual gas revenues are substantially realized during the heating season as a result of higher sales of natural gas due to cold weather. Accordingly, the results of operations are historically most favorable in the first and fourth quarters. Fluctuations in seasonal weather conditions may have a significant effect on the results of operations. Sales of electricity are generally less sensitive to weather than natural gas sales, but also may be affected by the weather conditions in both the winter and summer seasons.

Use of GAAP and Non-GAAP Financial Measures

The MD&A includes financial information prepared in accordance with GAAP, as well as certain non-GAAP financial measures. The Company's management believes that the non-GAAP presentations of earnings and Earnings Per Share (EPS) and Electric and Gas Adjusted Gross Margins are a more meaningful representation of the Company's financial performance and provide additional and useful information to readers of this report in analyzing the historical and future performance of the business. The non-GAAP financial measures should be viewed as a supplement to, and not a substitute for, financial measures presented in accordance with GAAP. Non-GAAP measures as presented herein may not be comparable to similarly titled measures used by other companies.

The Company's earnings discussion includes Adjusted Net Income, a non-GAAP financial measure referencing the Company’s 2026 and 2025 GAAP Net Income adjusted for certain transaction costs related to the Company's acquisitions of Bangor Natural Gas Company (purchase completed as of January 31, 2025), Maine Natural Gas Corporation (purchase completed as of October 31, 2025), Aquarion Water Company of New Hampshire, Inc., and Abenaki Water Co., Inc. (the Aquarion Companies) (purchase completed as of June 30, 2026). The Company's management believes that the transaction costs related to the acquisitions of Bangor, Maine Natural and the Aquarion Companies, which are included in Operation and Maintenance expense on the Consolidated Statements of Earnings, are not indicative of the Company's ongoing costs and not directly related to the ongoing operations of the business and therefore are not an indicator of baseline operating performance.

Reconciliation of Adjusted Net Income to GAAP Net Income

In the following tables, the Company has reconciled Adjusted Net Income to GAAP Net Income, which we believe to be the most comparable GAAP financial measure.

The Company analyzes operating results using Electric and Gas Adjusted Gross Margins, which are non-GAAP financial measures. Electric Adjusted Gross Margin is calculated as Total Electric Operating Revenue less Cost of Electric Sales. Gas Adjusted Gross Margin is calculated as Total Gas Operating Revenues less Cost of Gas Sales. The Company’s management believes Electric and Gas Adjusted Gross Margins provide useful information to investors regarding profitability. Also, the Company’s management believes Electric and Gas Adjusted Gross Margins are important financial measures to analyze revenue from the Company’s ongoing operations because the approved cost of electric and gas sales are tracked, reconciled and passed through directly to customers in electric and gas tariff rates, resulting in an equal and offsetting amount reflected in Total Electric and Gas Operating Revenue.

In the following tables, the Company has reconciled Electric and Gas Adjusted Gross Margin to GAAP Gross Margin, which we believe to be the most comparable GAAP financial measure. GAAP Gross Margin is calculated as Revenue less Cost of Sales and Depreciation and Amortization. The Company calculates Electric and Gas Adjusted Gross Margin as Revenue less Cost of Sales. The Company believes excluding Depreciation and Amortization, which are period costs and not related to volumetric sales, is a meaningful measure to inform investors of the Company’s profitability from electric and gas sales in the period.

Electric GAAP Gross Margin was $26.1 million in the three months ended September 30, 2026, an increase of $1.0 million compared to the same period in 2025. Electric GAAP Gross Margin was $70.4 million in the nine months ended September 30, 2026, an increase of $7.7 million compared to the same period in 2025. The three-month period increase was driven by higher rates and customer growth of $1.7 million, partially offset by higher depreciation and amortization expense of $0.7 million. The nine-month period increase was driven by higher rates of $10.3 million, partially offset by higher depreciation and amortization expense of $1.9 million and a one-time reduction of FERC transmission revenue of $0.7 million (see Note 7 Regulatory Matters: FERC Transmission Formula Rate Proceedings).

Gas GAAP Gross Margin was $13.5 million in the three months ended September 30, 2026, an increase of $1.1 million compared to the same period in 2025. Gas GAAP Gross Margin was $105.6 million in the nine months ended September 30, 2026, an increase of $12.9 million compared to the same period in 2025. The increase in the three-month period was driven by higher rates and customer growth of $2.6 million, partially offset by higher depreciation and amortization of $1.5 million. The increase in the nine-month period was driven by higher rates and customer growth of $15.8 million, the favorable effects of colder winter weather in 2026 of $1.4 million, partially offset by higher depreciation and amortization of $4.3 million. Included in gas operating revenue, cost of gas sales and depreciation and amortization for the three months ended September 30, 2026 was $2.9 million, $1.1 million and $0.9 million, respectively, related to Maine Natural. Included in gas operating revenue, cost of gas sales and depreciation and amortization for the nine months ended September 30, 2026 was $25.4 million, $14.9 million and $2.4 million, respectively, related to Maine Natural.

Earnings Overview

The Company’s Net Income (Loss) was ($1.5) million, or ($0.08) in EPS for the third quarter of 2026, a decrease of $1.2 million in Net Income, or $0.06 in EPS, compared to the third quarter of 2025. The Company's Adjusted Net Income (Loss) (a non-GAAP financial measure), which excluded transaction-related costs in connection with the acquisitions of Bangor, Maine Natural and the Aquarion Companies, was ($0.7) million, or ($0.04) in EPS for the third quarter of 2026, a decrease of $1.1 million, or $0.07 in EPS, when compared to the third quarter of 2025.

The Company’s Net Income was $36.4 million, or $2.02 in EPS for the first nine months of 2026, an increase of $5.2 million in Net Income, or $0.13 in EPS, compared to the first nine months of 2025. The Company's Adjusted Net Income (a non-GAAP financial measure), which excluded transaction-related costs in connection with the acquisitions of Bangor, Maine Natural and the Aquarion Companies, was $38.3 million, or $2.12 in EPS for the first nine months of 2026, an increase of $4.8 million, or $0.09 in EPS, when compared to the first nine months of 2025.

Electric Adjusted Gross Margin (a non-GAAP financial measure) was $34.8 million and $96.0 million in the three and nine months ended September 30, 2026, respectively, increases of $1.7 million and $9.6 million, respectively, compared to the same periods in 2025. The increase in the three-month period reflects higher rates and customer growth of $1.7 million. The increase in the nine-month period reflects higher rates of $10.3 million, partially offset by a one-time reduction of FERC transmission revenue of $0.7 million (see Note 7 Regulatory Matters: FERC Transmission Formula Rate Proceedings).

Gas Adjusted Gross Margin (a non-GAAP financial measure) was $29.2 million and $151.9 million in the three and nine months ended September 30, 2026, respectively, increases of $2.6 million and $17.2 million, respectively, compared to the same periods in 2025. The increase in the three-month period reflects higher rates and customer growth of $2.6 million. The increase in the nine-month period was driven by higher rates and customer growth of $15.8 million and the favorable effects of colder winter weather in 2026 of $1.4 million. Included in the Gas Adjusted Gross Margin for the three and nine months ended September 30, 2026 was $1.8 million and $10.5 million, respectively, related to Maine Natural.

Water Revenues were $3.1 million for the three and nine months ended September 30, 2026. There were no Water Revenues recognized for the three and nine months ended September 30, 2025 as the acquisitions of the AWC-NH and Abenaki closed on June 30, 2026. Please see Note 1 (Summary of Significant Accounting Policies: Acquisition of the Aquarion Water Companies) for additional details.

Operation and Maintenance (O&M) expenses increased $4.9 million and $8.2 million in the three and nine months ended September 30, 2026, respectively, compared to the same periods in 2025. The increase in the three-month period reflects higher utility operating costs of $2.6 million, higher labor and other costs of $2.2 million and higher acquisition costs of $0.1 million. The increase in the nine-month period reflects higher utility operating costs of $5.1 million, and higher labor and other costs of $3.8 million, partially offset by lower acquisition costs of $0.7 million. Included in O&M expenses for the three and nine months ended September 30, 2026 were $1.2 million and $3.9 million, respectively, related to Maine Natural and $1.2 million and $1.2 million, respectively, related to the Aquarion Companies. Excluding O&M expenses for Maine Natural, the Aquarion Companies and transaction costs, O&M expenses for legacy operations would have increased by $2.4 million and $3.8 million for the three and nine months ended September 30, 2026, respectively.

Depreciation and Amortization expense increased $2.6 million and $6.6 million in the three and nine months ended September 30, 2026, respectively, compared to the same periods in 2025. The increase in the three-month period reflects higher levels of utility plant in service, and higher amortization of recoverable storm costs and other deferred costs. The increase in the nine-month period reflects higher levels of utility plant in service and higher amortization of recoverable storm costs, partially offset by lower amortization of other deferred costs. Included in Depreciation and Amortization for the three and nine months ended September 30, 2026 was $0.9 million and $2.4 million, respectively, related to Maine Natural and $0.4 million and $0.4 million, respectively, related to the Aquarion Companies.

Taxes Other Than Income Taxes increased $0.1 million and $3.5 million in the three and nine months ended September 30, 2026, respectively, compared to the same periods in 2025. These increases reflect higher local property taxes on higher utility plant in service and higher payroll taxes. Included in Taxes Other Than Income Taxes for the three and nine months ended September 30, 2026 were $0.5 million and $1.3 million, respectively, related to Maine Natural and $0.2 million and $0.2 million, respectively, related to the Aquarion Companies.

Interest Expense, Net increased $2.1 million and $4.9 million in the three and nine months ended September 30, 2026, respectively, compared to the same periods in 2025, primarily reflecting higher levels of short-term borrowings and long-term debt, partially offset by lower interest expense for regulatory liabilities.

Other Expense (Income), Net decreased $0.7 million and $0.9 million in the three and nine months ended September 30, 2026, respectively, compared to the same periods in 2025, primarily from lower retirement benefit costs.

Provision for (Benefit from) Income Taxes increased $0.4 million in the three months ended September 30, 2026, compared with the same period in 2025, reflecting higher pre-tax loss in 2026. Provision for (Benefit from) Income Taxes increased $2.4 million in the nine months ended September 30, 2026, compared with the same period in 2025, reflecting higher pre-tax earnings in 2026.

At its January 2026, April 2026, July 2026 and October 2026 meetings, the Unitil Corporation Board of Directors declared quarterly dividends on the Company’s common stock of $0.475 per share. These quarterly dividends result in a current effective annualized dividend rate of $1.90 per share, representing an unbroken record of quarterly dividend payments since trading began in Unitil’s common stock.