UNITIL CORPORATION 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 of1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject tosuch filing requirements for the past 90 days.Yes☒No☐ Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reportingcompany, 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 withany 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. Class Table of Contents Cautionary Statement Part I. Financial Information Item 1.Financial Statements—UnauditedConsolidated Statements of Earnings—Three Months Ended March 31, 2025 and 2024134Consolidated Balance Sheets—March 31, 2025, March 31, 2024 and December 31, 202414-15Consolidated Statements of Cash Flows—Three Months Ended March 31, 2025 and 202416Consolidated Statements of Changes in Common Stock Equity – Three Months EndedMarch 31, 2025 and 202417Notes to Consolidated Financial Statements18-43Item 2.Management’s Discussion and Analysis (MD&A) of Financial Condition and Results ofOperations3-12Item 3.Quantitative and Qualitative Disclosures About Market Risk44Item 4.Controls and Procedures44 Part II. Other Information Item 1.Legal Proceedings44Item 1A.Risk Factors44 Item 5.Other InformationItem 6.ExhibitsSignatures 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 SecuritiesAct), Section 21E of the Securities Exchange Act of 1934, as amended (the Exchange Act), and the Private 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 othercomparable terminology. These forward-looking statements are subject to inherent risks and uncertainties inpredicting future results and conditions that could cause the actual results to differ materially from those projected in •numerous hazards and operating risks relating to the Company’s electric and natural gas distributionactivities, which could result in accidents and other operating risks and costs; •fluctuations in the supply of, demand for, and the prices of, electric and gas energy commodities andtransmission and transportation capacity and the Company’s ability to recover energy supply costs inits rates; •catastrophic events; •cyber-attacks, acts of terrorism, acts of war, severe weather, a solar event, an electromagnetic event, anatural disaster, the age and condition of information technology assets, human error, or other factorscould disrupt the Company’s operations and cause the Company to incur unanticipated losses andexpense; •outsourcing of services to third parties could expose the Company to substandard quality of servicedelivery or substandard deliverables, which may result in missed deadlines or other timeliness issues,non-compliance (including with applicable legal requirements and industry standards) or reputational •unforeseen or changing circumstances, which could adversely affect the reduction of Company-widedirect greenhouse gas emissions; •the Company’s regulatory and legislative environment (including laws and regulations relating toclimate change, greenhouse gas emissions and other environmental matters) could affect the rates theCompany is able to charge, the Company’s authorized rate of return, the Company’s ability to recover •general economic conditions, which could adversely affect (i) the Company’s customers and,consequently, the demand for the Company’s distribution services, (ii) the availability of credit and •the Company’s ability to obtain debt or equity financing on acceptable terms; •increases in interest rates, which could increase the Company’s interest expense; •the Company's payment of dividends in the future; •declines in capital market valuations, which could require the Company to make substantial cashcontributions to cover its pension obligati