A city or town, including a code city, that owns or operates an electric or gas utility may waive connection charges for properties purchased by low-income persons from organizations exempt from tax under section 501(c)(3) of the federal internal revenue code as amended prior to July 23, 1995. Waivers of connection charges for the same class of electric or gas utility service must be uniformly applied to all qualified property. Nothing in this section authorizes the impairment of a contract.