This Seventeenth Supplemental Indenture is dated as of August 21, 2024 (the or this
Seventeenth Supplemental Indenture) and entered into by and between Unitil Energy Systems, Inc., a corporation duly organized and existing under and by virtue of the laws of the State of New Hampshire, having its principal office and
place of business in Hampton, County of Rockingham in the State of New Hampshire at 6 Liberty Lane West, Hampton, New Hampshire 03842-1720 (hereinafter sometimes referred to as the Company), and U.S. Bank Trust Company, National
Association (as successor to U.S. Bank National Association), a national banking association, having an office and place of business in Boston, Massachusetts at 1 Federal Street, Boston, Massachusetts 02110, as Trustee (hereinafter sometimes
referred to as the Trustee), with reference to the following Recitals:
W I T N
E S S E T H:
Whereas, the Company
heretofore duly executed and delivered to the Trustee its Indenture of Mortgage and Deed of Trust (hereinafter generally referred to as the Original Indenture and referred to, with each and every other instrument, including the Twelfth
Supplemental Indenture, which amended and restated the Original Indenture in its entirety, and each subsequent instrument which the Company may execute with the Trustee and which is therein stated to be supplemental to the Original Indenture, as the
Indenture), dated as of July 15, 1958, but actually executed on September 18, 1958, and recorded, among other places, in Merrimack County, New Hampshire, Registry of Deeds, Volume 832, Page 96, and in the Office of
the City Clerk of the City of Concord, New Hampshire, Volume 188, Page 156 and duly recorded First, Second, Third, Fourth, Fifth, Sixth, Seventh, Eighth, Ninth, Tenth, Eleventh, Twelfth, Thirteenth, Fourteenth, Fifteenth, and Sixteenth
Supplemental Indentures thereto dated as of January 15, 1968, as of November 15, 1971, as of July 1, 1975, as of March 28, 1984, as of June 1, 1984, as of October 29, 1987, as of August 29, 1991, as of
October 14, 1994, as of September 1, 1998, as of January 15, 2001, as of April 20, 2001, as of December 2, 2002, as of September 26, 2006, as of March 2, 2010, as of November 29, 2018, and as of
September 15, 2020, respectively, to which this instrument is supplemental and in modification and confirmation thereof, whereby substantially all the properties of the Company used by it in its electric business, whether then owned or
thereafter acquired, with certain exceptions and reservations fully set forth in the Indenture were given, granted, bargained, sold, warranted, pledged, assigned, transferred, mortgaged and conveyed to the Trustee, its successors and assigns, in
trust upon the terms and conditions set forth therein to secure bonds of the Company issued and to be issued thereunder, and for other purposes more particularly specified therein; and
Whereas, on January 4, 1971 Old Colony Trust Company was merged into The First National Bank of Boston, which thereupon succeeded to the
trusts under the Indenture; and
Whereas, effective May 1, 1996 The First National Bank of Boston resigned as trustee under the
Indenture and the Company appointed State Street Bank and Trust Company (State Street) as successor trustee, which accepted such appointment and thereupon succeeded to the trusts under the Indenture; and
Whereas, effective January 1, 2003 U.S. Bank National Association purchased substantially all of the corporate trust business of State
Street including the trust herein and thereupon succeeded State Street as Trustee hereunder; and
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