Any irrigation district engaged in the distribution of energy is hereby authorized, within limits established by the Constitution of the state of Washington, to assist the owners of residential structures in financing the acquisition and installation of materials and equipment, for compensation or otherwise, for the conservation or more efficient use of energy in such structures pursuant to an energy conservation plan adopted by the irrigation district if the cost per unit of energy saved or produced by the use of such materials and equipment is less than the cost per unit of energy produced by the next least costly new energy resource which the irrigation district could acquire to meet future demand. Except where otherwise authorized, such assistance shall be limited to:

(1) Providing an inspection of the residential structure, either directly or through one or more inspectors under contract, to determine and inform the owner of the estimated cost of purchasing and installing conservation materials and equipment for which financial assistance will be approved and the estimated life-cycle savings in energy costs that are likely to result from the installation of such materials or equipment.

(2) Providing a list of businesses who sell and install such materials and equipment within or in close proximity to the service area of the irrigation district, each of which businesses shall have requested to be included and shall have the ability to provide the products in a workmanlike manner and to utilize such materials in accordance with the prevailing national standards.

(3) Arranging to have approved conservation materials and equipment installed by a private contractor whose bid is acceptable to the owner of the residential structure and verifying such installation.

(4) Arranging or providing financing for the purchase and installation of approved conservation materials and equipment. Such materials and equipment shall be purchased from a private business and shall be installed by a private business or the owner.

(5) Pay back shall be in the form of incremental additions to the utility bill, billed either together with use charge or separately. Loans shall not exceed two hundred forty months in length.