Wash. Rev. Code § 35.97.030
A municipality may construct, purchase, acquire, add to, extend, maintain, and operate a system of heating facilities, within or without its limits, for the purpose of supplying its inhabitants and other persons with heat, with full power to regulate and control the use, distribution, and price of supplying heat, and to enter into agreements for the maintenance and operation of heating facilities under terms and conditions determined by the legislative authority of the municipality. The provision of heat and heating facilities and the establishment and operation of heating systems by a municipality under this chapter are hereby declared to be a public use and a public and strictly municipal purpose. However, nothing in this chapter shall be construed to restrain or limit the authority of any individual, partnership, corporation, or private utility from establishing and operating heating systems.
RCW 35.97.030