(a) The standards proposed by the department pursuant to Section 17921 may include voluntary best practice and mandatory requirements related to environmentally preferable water using devices and measures. The standards shall not unreasonably or unnecessarily impact the ability of Californians to purchase or rent affordable housing, as determined by taking account of the overall benefit derived from the standards.
(b) Nothing in this section shall in any way reduce the authority of the State Energy Resources Conservation and Development Commission to adopt standards and regulations or take other actions pursuant to Division 15 (commencing with Section 25000) of the Public Resources Code.