Civ. Code, § 8802

(a) This section applies to a contract between a public utility and a direct contractor for all or part of a work of improvement.

(b) Unless the direct contractor and a subcontractor otherwise agree in writing, within 21 days after receipt of a progress payment from the public utility the direct contractor shall pay the subcontractor the amount allowed the direct contractor on account of the work performed by the subcontractor to the extent of the subcontractor’s interest in the work. If there is a good faith dispute over all or part of the amount due on a progress payment from the direct contractor to a subcontractor, the direct contractor may withhold an amount not in excess of 150 percent of the disputed amount.

(c) A direct contractor that violates this section is liable to the subcontractor for a penalty of 2 percent of the disputed amount due per month for every month that payment is not made. In an action for collection of the amount wrongfully withheld, the prevailing party is entitled to costs and a reasonable attorney’s fee.

(d) This section does not limit or impair a contractual, administrative, or judicial remedy otherwise available to a contractor or subcontractor in a dispute involving late payment or nonpayment by the contractor or deficient performance or nonperformance by the subcontractor.