Business Description

UNITIL CORPORATION In this Annual Report on Form 10-K, the “Company”, “Unitil”, “we”, and “our” refer to Unitil Corporation and its subsidiaries, unless the context requires otherwise. Unitil is a public utility holding company incorporated under the laws of the State of New Hampshire in 1984. The following companies are wholly-owned subsidiaries of Unitil: Company Name State and Year of Organization Principal Business Unitil Energy Systems, Inc. (Unitil Energy) NH - 1901 Electric Distribution Utility Fitchburg Gas and Electric Light Company (Fitchburg) MA - 1852 Electric & Natural Gas Distribution Utility Northern Utilities, Inc. (Northern Utilities) NH - 1979 Natural Gas Distribution Utility Bangor Natural Gas Company (Bangor) ME - 1998 Natural Gas Distribution Utility Maine Natural Gas Corporation (Maine Natural) ME - 1998 Natural Gas Distribution Utility Granite State Gas Transmission, Inc. (Granite State) NH - 1955 Natural Gas Transmission Pipeline Unitil Power Corp. (Unitil Power) NH - 1984 Wholesale Electric Power Utility Unitil Service Corp. (Unitil Service) NH - 1984 Utility Service Company Unitil Realty Corp. (Unitil Realty) NH - 1986 Real Estate Management Unitil Resources, Inc. (Unitil Resources) NH - 1993 Non-regulated Energy Services Unitil Water Corp. (Unitil Water) NH - 2025 Non-regulated 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. Unitil’s principal business is the local distribution of electricity and natural gas to approximately 215,100 customers throughout its service territories in the states of New Hampshire, Massachusetts and Maine. Unitil is the parent company of five wholly-owned distribution utilities: i) Unitil Energy, which provides electric service in the southeastern seacoast and state capital regions of New Hampshire, including the capital city of Concord, ii) Fitchburg, which provides both electric and natural gas service in the greater Fitchburg area of north central Massachusetts, iii) Northern Utilities, which provides natural gas service in southeastern New Hampshire and portions of southern and central Maine, including the city of Portland, which is the largest city in northern New England, iv) Bangor, which provides natural gas service in the Bangor area of central Maine, and v) Maine Natural, which provides natural gas service in southern and central Maine, including the greater Portland region, as well as the capital city of Augusta. In addition, Unitil is the parent company of Granite State, an interstate natural gas transmission pipeline company that provides interstate natural gas pipeline access and transportation services to Northern Utilities in its New Hampshire and Maine service territory. Together, Unitil’s five distribution utilities serve approximately 110,100 electric customers and 105,000 natural gas customers. Customers Served as of December 31, 2025 Residential Commercial & Industrial (C&I) Total Electric: Unitil Energy 67,879 11,532 79,411 Fitchburg 26,422 4,231 30,653 Total Electric 94,301 15,763 110,064 Natural Gas: Northern Utilities 56,094 17,161 73,255 Fitchburg 14,706 1,735 16,441 Bangor 7,162 1,751 8,913 Maine Natural 4,803 1,650 6,453 Total Natural Gas 82,765 22,297 105,062 Total Customers Served 177,066 38,060 215,126 Unitil had an investment in Net Utility Plant of $1.8 billion at December 31, 2025. The Company’s total operating revenue was $536.0 million in 2025. Unitil’s operating revenue is substantially derived from regulated electric and natural gas distribution utility operations. A seventh utility subsidiary, Unitil Power, formerly functioned as the full requirements wholesale 3 Table of Contents 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 has four other wholly-owned non-utility subsidiaries: Unitil Service, Unitil Realty, Unitil Resources and Unitil Water. Unitil Service provides, at cost, a variety of administrative and professional services, including regulatory, financial, accounting, human resources, engineering, operations, technology and energy supply management services on a centralized basis to its affiliated Unitil companies.…