Okla. Stat. tit. 68, § 68-2357.1: Solar energy system defined

As used in this section and Section 2357.2 of this title, "solar

energy system" means a system primarily designed to provide heating

or cooling, electrical or mechanical power, or any combination

thereof by means of collecting, transferring or storing solar

generated energy for such purposes. Such term shall include passive

structural and nonstructural features which are designed to provide

a calculated net energy gain to a structure from renewable energy

sources, commonly referred to as "passive solar energy systems", but

shall not include those parts of a structural system which would be

required regardless of the energy source being utilized. Solar

energy may be derived from either direct processes or indirect

processes using wind energy systems.