(A) There is allowed as a tax credit against the income tax liability of a taxpayer imposed by this chapter an amount equal to twenty-five percent of the costs incurred by the taxpayer in the installation of a solar energy heating or cooling system, or both, in a building owned by the taxpayer. The tax credit allowed by this section must not be claimed before the completion of the installation, and must be claimed for the year that the costs are incurred. The amount of the credit may not exceed three thousand five hundred dollars or fifty percent of the taxpayer's tax liability for that taxable year, whichever is less. If the amount of the credit exceeds three thousand five hundred dollars, the taxpayer may carry forward the excess for up to ten years.
(B) "System" includes all controls, tanks, pumps, heat exchangers, and other equipment used directly and exclusively for the conversion of solar energy for heating or cooling. The term "system" does not include any land or structural elements of the building such as walls and roofs or other equipment ordinarily contained in the structure.