POWER OF ATTORNEY

            KNOW ALL BY THESE PRESENTS, that the undersigned, Meghan Nutting,
hereby constitutes and appoints Walter A. Baker and Margaret C. Fitzgerald, each
signing individually, 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 and/or director of Sunnova Energy
            International 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
            Form 3, 4 or 5 and timely file such form with the United States
            Securities and Exchange Commission and any stock exchange or similar
            authority; and

        3.  take any other action of any type whatsoever in connection with the
            foregoing which, in the opinion of such attorney-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
            attorney-in-fact on behalf of the undersigned pursuant to this Power
            of Attorney shall be in such form and shall contain such terms and
            conditions as such attorney-in-fact may approve in such attorney-in-
            fact's discretion.

            The undersigned hereby grants to each such attorney-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
substitution or revocation, hereby ratifying and confirming all that such
attorney-in-fact, or such attorney-in-fact's substitute or substitutes, 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 the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, are not assuming, nor is the Corporation assuming, any of the
undersigned's responsibilities to comply with Section 16 of the Securities
Exchange Act of 1934.

            This Power of Attorney shall remain in full force and effect until
the undersigned is no longer required to file Forms 3, 4 or 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.

     IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 11th day of July, 2019.


                                     By: /s/ Meghan Nutting
                                         ---------------------------------------
                                     Name: Meghan Nutting