California Law provides a property tax exemption for qualified solar energy systems.

California Revenue and Taxation Code, section 73.

(a) Pursuant to the authority granted to the Legislature pursuant to paragraph (1) of subdivision (c) of Section 2 of Article XIIIA of the California Constitution, the term "newly constructed," as used in subdivision (a) of Section 2 of Article XIIIA of the California Constitution, does not include the construction or addition of any active solar energy system, as defined in subdivision (b).

(b) (1) "Active solar energy system" means a system that uses solar devices, which are thermally isolated from living space or any other area where the energy is used, to provide for the collection, storage, or distribution of solar energy. (2) "Active solar energy system" does not include solar swimming pool heaters or hot tub heaters. (3) Active solar energy systems may be used for any of the following: (A) Domestic, recreational, therapeutic, or service water heating.   (B) Space conditioning. (C) Production of electricity. (D) Process heat. (E) Solar mechanical energy.

(c) (1) (A) The Legislature finds and declares that the definition of spare parts in this paragraph is declarative of the intent of the Legislature, in prior statutory enactments of this section that excluded active solar energy systems from the term "newly constructed," as used in the California Constitution, thereby creating a tax appraisal exclusion. (B) An active solar energy system that uses solar energy in the production of electricity includes storage devices, power conditioning equipment, transfer equipment, and parts related to the functioning of those items. In general, the use of solar energy in the production of electricity involves the transformation of sunlight into electricity through the use of devices such as solar cells or other collectors. However, an active solar energy system used in the production of electricity includes only equipment used up to, but not including, the stage of the transmission or use of the electricity. For the purpose of this paragraph, the term "parts" includes spare parts that are owned by the owner of, or the maintenance contractor for, an active solar energy system that uses solar energy in the production of electricity and which spare parts were specifically purchased, designed, or fabricated by or for that owner or maintenance contractor for installation in an active solar energy system that uses solar energy in the production of electricity, thereby including those parts in the tax appraisal exclusion created by this section. (2) An active solar energy system that uses solar energy in the production of electricity also includes pipes and ducts that are used exclusively to carry energy derived from solar energy. Pipes and ducts that are used to carry both energy derived from solar energy and from energy derived from other sources are active solar energy system property only to the extent of 75 percent of their full cash value. (3) An active solar energy system that uses solar energy in the production of electricity does not include auxiliary equipment, such as furnaces and hot water heaters, that use a source of power other than solar energy to provide usable energy. An active solar energy system that uses solar energy in the production of electricity does include equipment, such as ducts and hot water tanks, that is utilized by both auxiliary equipment and solar energy equipment, that is, dual use equipment. That equipment is active solar energy system property only to the extent of 75 percent of its full cash value.

(d) This section applies to property tax lien dates for the 1999-2000 fiscal year to the 2008-09 fiscal year, inclusive. For purposes of supplemental assessment, this section applies only to qualifying construction or additions completed on or after January 1, 1999.

(e) This section shall remain in effect only until January 1, 2010, and as of that date is repealed.