POWER OF ATTORNEY

        KNOW ALL MEN BY THESE PRESENTS, that the undersigned hereby constitutes
and appoints Joseph L. McCormick, Senior Vice President, General Counsel and
Assistant Secretary and Brian K. Shore, Vice President, Associate General
Counsel and Secretary, the undersigned's true and lawful attorneys-in-fact to:

(1)     Execute for and on behalf of the undersigned, in the undersigned's
        capacity as an officer of ONE Gas, Inc. (the Corporation), Forms 3,
        4, and 5 in accordance with Section 16(a) of the Securities Exchange
        Act of 1934 and the rules thereunder;

(2)     Do and perform any and all acts for and on behalf of the undersigned
        which may be necessary or desirable to complete and execute any such
        Forms 3, 4, or 5 and timely file such form with the United States
        Securities and Exchange Commission and any stock exchange or similar
        authority;

(3)     Take any other action of any type whatsoever in connection with the
        foregoing which, in the opinion of such attorneys-in-fact, may be of
        benefit to, in the best interest of, or legally required by the
        undersigned, it being understood that the documents executed by such
        attorneys-in-fact on behalf of the undersigned pursuant to this Power
        of Attorney shall be in such form and shall contain the terms and
        conditions as such attorneys-in-fact may approve in such attorneys-in-
        fact's discretion.

        The undersigned hereby grants to each such attorneys-in-fact full power
and authority to do and perform any and every act and thing whatsoever
requisite, necessary, or proper to be done in the exercise of any of the rights
and powers herein granted, as fully to all intents and purposes as the
undersigned might or could do if personally present, with full power of
revocation, hereby ratifying and confirming all that each such attorneys-in-
fact shall lawfully do or cause to be done by virtue of this power of attorney
and the rights and powers herein granted. The undersigned acknowledges that
neither the Corporation nor the above-named individuals, in serving in such
capacity at the request of the undersigned, are assuming any of the
undersigned's responsibilities to comply with Section 16 of the Securities
Exchange Act of 1934.

        The Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4, and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the
Corporation, unless earlier revoked by the undersigned in a signed writing
delivered to the foregoing attorneys-in-fact. This Power of Attorney revokes
all such special powers of attorney granted to individuals in the past to act
on behalf of the undersigned for the purposes stated above.

        IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney
to be executed as of this 30th day of June 2023.

                                   /s/ Deborah A.P. Hersman
                                   -------------------------------
                                   Deborah A.P. Hersman

                                 CONFIRMING STATEMENT

        This Statement confirms that the undersigned has authorized and
designated Joseph L. McCormick, Senior Vice President,General Counsel and
Assistant Secretary, and Brian K. Shore, Vice President, Associate General
Counsel and Secretary, to execute and file on the undersigned's behalf all
Forms 3, 4, and 5 (including any amendments thereto) that the undersigned may
be required to file with the United States Securities and Exchange Commission
as a result of the undersigned's ownership of or transactions in securities of
ONE Gas, Inc. The authority of the above-named individuals under this Statement
shall continue until the undersigned is no longer required to file Forms 3, 4,
or 5 with regard to the undersigned's ownership of or transactions in
securities of ONE Gas, Inc. unless earlier revoked in writing. This Statement
revokes all such special powers of attorney granted to individuals in the past
to act on behalf of the undersigned for the purposes stated above. The
undersigned acknowledges that neither ONE Gas, Inc. nor the above-named
individuals are assuming any of the undersigned's responsibilities to comply
with Section 16 of the Securities Exchange Act of 1934.


                                   /s/ Deborah A.P. Hersman
                                   -------------------------------
                                   Deborah A.P. Hersman

Dated: June 30, 2023