N.Y. Pub. Auth. Law § 1020-F
Whenever any electrical energy which the authority may acquire creates a surplus over the amount of light, heat and power, in any of such services, required by the residents of the district to which such service is contracted, the authority may sell such surplus in territory outside the district to persons or public or private corporations. In acquiring any facility or property which also serves any municipality or territory outside the district, the authority, if it deems it advantageous and economical so to do, may, with the consent of the board of trustees, serve any such municipality or territory or sell heat, power or electrical energy to persons, public or private corporations in such territory or to such municipality.
N.Y. Pub. Auth. Law § 1020-F