Cal. Fin. Code § 1495

(a) A commercial bank may make amortized loans upon the security of residential real property to finance the purchase and installation of material or equipment designed to promote energy conservation or the efficient use of energy in the residential real property securing the loan, if, (1) The residential real property securing the loan consists of not more than four dwelling units; (2) The loan is made in connection with a concurrent loan authorized under Section 1486; and (3) The loan is in an amount not to exceed 10 percent of the loan made under the authority of Section 1486.

(b) A commercial bank may make additional advances, or additional loans, to an existing borrower in order to finance the purchase and installation of material and equipment designed to promote energy conservation or the efficient use of energy in the residential real property securing the loan, if, (1) The residential real property securing the loan consists of not more than four dwelling units; and (2) The aggregate of the additional loan or advance and the unpaid balance of the existing loan will not exceed that percent of the appraised value of the residential real property securing the loan permitted by Section 1227 immediately after the purchase and installation of such material and equipment.