Health & Saf. Code, § 43804

(a) If a low-emission motor vehicle meets the requirements of this chapter and the performance, cost, service, and maintenance requirements adopted by the Department of General Services for such motor vehicles, and if funds are appropriated for the purpose of purchasing motor vehicles, the state shall purchase, beginning with the next fiscal year, as many of such low-emission motor vehicles as the Department of General Services determines are reasonable and available to meet state needs.

(b) If a sufficient number of low-emission motor vehicles are available, the percentage of all such motor vehicles to be purchased in that year shall not be less than 25 percent of all motor vehicles purchased by the state in the preceding fiscal year. In purchasing vehicles pursuant to this section, the state shall seek to acquire a mix of least polluting and least cost qualifying low-emission motor vehicles.