(a) As used in this Code section, the term "local authority" means an instrumentality of one or more local governments created to fulfill a specialized public purpose or any other legally created organization that has authority to issue debt for a public purpose independent of a county or municipality, regardless of name; provided, however, that the term "local authority" does not include a state authority. A local authority may have been created by local constitutional amendment, general statute, or local law.

(b) The governing body of any local authority which is authorized to provide electric, natural gas, or water utility services in this state may authorize the execution of one or more contracts which specify the rates, fees, or other charges which will be charged and collected by the local authority for electric, natural gas, or water utility services to be provided by the local authority to one or more of its utility customers. Any such contract shall be subject to the following conditions and limitations:

(1) No such contract shall be for a term in excess of ten years;

(2) Any such contract which is for a term in excess of two years shall include commercially reasonable provisions under which the rates, fees, or other charges shall be adjusted with respect to inflationary or deflationary factors affecting the provision of the utility service in question; and

(3) Any such contract shall include commercially reasonable provisions relieving the local authority from its obligations under the contract in the event that the local authority's ability to comply with the contract is impaired by war, natural disaster, catastrophe, or any other emergency creating conditions under which the local authority's compliance with the contract would become impossible or create a substantial financial burden upon the local authority or its taxpayers.