(1) An electrical, gas, or water company may file a conservation service tariff with the commission. The tariff shall provide:

(a) The terms and conditions upon which the company will offer the conservation measures and services specified in the tariff;

(b) The period of time during which the conservation measures and services will be offered; and

(c) The maximum amount of expenditures to be made during a specified time period by the company on conservation measures and services specified in the tariff.

(2) The commission has the same authority with respect to a proposed conservation service tariff as it has with regard to any other schedule or classification the effect of which is to change any rate or charge, including, without limitation, the power granted by RCW 80.04.130 to conduct a hearing concerning a proposed conservation service tariff and the reasonableness and justness thereof, and pending such hearing and the decision thereon the commission may suspend the operation of the tariff for a period not exceeding ten months from the time the tariff would otherwise go into effect.

(3) An electrical, gas, or water company may from time to time apply to the commission for a determination that specific expenditures may under its tariff constitute bondable conservation investment. A company may request this determination by the commission in separate proceedings for this purpose or in connection with a general rate case. The commission may designate the expenditures as bondable conservation investment as defined in RCW 80.28.005(1) if it finds that such designation is in the public interest.

(4) The commission shall include in rate base all bondable conservation investment. The commission shall approve rates for service by electrical, gas, and water companies at levels sufficient to recover all of the expenditures of the bondable conservation investment included in rate base and the costs of equity and debt capital associated therewith, including, without limitation, the payment of principal, premium, if any, and interest on conservation bonds. The rates so determined may be included in general rate schedules or may be expressed in one or more separate rate schedules. The commission shall not revalue bondable conservation investment for rate-making purposes, to determine that revenues required to recover bondable conservation investment and associated equity and debt capital costs are unjust, unreasonable, or in any way impair or reduce the value of conservation investment assets or that would impair the timing or the amount of revenues arising with respect to conservation investment assets that have been pledged to secure conservation bonds.

(5) Nothing in this chapter precludes the commission from adopting or continuing other conservation policies and programs intended to provide incentives for and to encourage utility investment in improving the efficiency of energy or water end use. However, the policies or programs shall not impair conservation investment assets. This chapter is not intended to be an exclusive or mandatory approach to conservation programs for electrical, gas, and water companies, and no such company is obligated to file conservation service tariffs under this chapter, to apply to the commission for a determination that conservation costs constitute bondable conservation investment within the meaning of this chapter, or to issue conservation bonds.

(6)(a) If a customer of an electrical, gas, or water company for whose benefit the company made expenditures for conservation measures or services ceases to be a customer of such company for one or more of the following reasons, the commission may require that the portion of such conservation expenditures that had been included in rate base but not theretofore recovered in the rates of such company be removed from the rate base of the company:

(i) The customer ceases to be a customer of the supplier of energy or water, and the customer repays to the company the portion of the conservation expenditures made for the benefit of such customer that has not theretofore been recovered in rates of the company; or

(ii) The company sells its property used to serve such customer and the customer ceases to be a customer of the company as a result of such action.

(b) An electrical, gas, or water company may include in a contract for a conservation measure or service, and the commission may by rule or order require to be included in such contracts, a provision requiring that, if the customer ceases to be a customer of that supplier of energy or water, the customer shall repay to the company the portion of the conservation expenditures made for the benefit of such customer that has not theretofore been recovered in rates of the company.