Washington state constitution
Article VIII
Section 10

Notwithstanding the provisions of section 7 of this Article, any county, city, town, quasi municipal corporation, municipal corporation, or political subdivision of the state which is engaged in the sale or distribution of water, energy, or stormwater or sewer services may, as authorized by the legislature, use public moneys or credit derived from operating revenues from the sale of water, energy, or stormwater or sewer services to assist the owners of structures or equipment in financing the acquisition and installation of materials and equipment for the conservation or more efficient use of water, energy, or stormwater or sewer services in such structures or equipment. Except as provided in section 7 of this Article, an appropriate charge back shall be made for such extension of public moneys or credit and the same shall be a lien against the structure benefited or a security interest in the equipment benefited. Any financing for energy conservation authorized by this article shall only be used for conservation purposes in existing structures and shall not be used for any purpose which results in a conversion from one energy source to another.