RCW 80.28.100

No gas company, electrical company, wastewater company, water company, or thermal energy company may, directly or indirectly, or by any special rate, rebate, drawback or other device or method, charge, demand, collect or receive from any person or corporation a greater or less compensation for gas, electricity, wastewater company services, water, or thermal energy, or for any service rendered or to be rendered, or in connection therewith, except as authorized in this chapter, than it charges, demands, collects or receives from any other person or corporation for doing a like or contemporaneous service with respect thereto under the same or substantially similar circumstances or conditions. If the commission finds any instance of a thermal energy resource provider injecting thermal energy into a thermal energy system that exceeds system needs and creates system imbalance, the commission may issue rules to address such an issue to ensure ratepayers are not charged for energy that does not provide a benefit.