Cal. Pub. Util. Code § 454.54

In addition to the requirements of Section 454.52, the integrated resource plan of each load-serving entity shall contribute to a diverse and balanced portfolio of resources needed to ensure a reliable electricity supply that provides optimal integration of renewable energy resources in a cost-effective manner, meets the emissions reduction targets for greenhouse gases described in subparagraph (A) of paragraph (1) of subdivision (a) of Section 454.52, and prevents cost shifting among load-serving entities.