California Code, Public Utilities Code - PUC § 2786

An electrical or gas corporation shall provide for payment by a customer for whom home insulation has been installed pursuant to this chapter through such periodic billing procedures as may be established by the corporation.  The corporation may require an initial payment toward the insulation services of not greater than 20 percent with the balance due payable in equal installments during a period of 36 months following completion of the work, or at such greater rate of repayment as the customer may elect.  Finance charges shall not be greater than the maximum allowable finance charges permitted for retail installment contracts.  Acceptable credit cards may be utilized in lieu of these financial arrangements.