Cal. Pub. Util. Code § 455.5

(a) In establishing rates for any electrical, gas, heat, or water corporation, the commission may eliminate consideration of the value of any portion of any electric, gas, heat, or water generation or production facility which, after having been placed in service, remains out of service for nine or more consecutive months, and may disallow any expenses related to that facility. Upon eliminating consideration of any portion of a facility or disallowing any expenses related thereto under this section, the commission shall reduce the rates of the corporation accordingly and shall, for accounting purposes, record the value of that portion of the facility in a deferred debit account and shall treat this amount similar to the treatment of the allowance for funds used during construction. When that portion of the facility is returned to useful service, as provided in subdivision (c), the corporation may apply to the commission for the inclusion of its value and expenses related to its operation for purposes of the establishment of the corporation’s rates.
(b) Every electrical, gas, heat, and water corporation shall periodically, as required by the commission, report to the commission on the status of any portion of any electric, gas, heat, or water generation or production facility which is out of service and shall immediately notify the commission when any portion of the facility has been out of service for nine consecutive months.
(c) Within 45 days of receiving the notification specified in subdivision (b), the commission shall institute an investigation to determine whether to reduce the rates of the corporation to reflect the portion of the electric, gas, heat, or water generation or production facility which is out of service. For purposes of this subdivision, out-of-service periods shall not include planned outages of predetermined duration scheduled in advance.
The commission’s order shall require that rates associated with that facility are subject to refund from the date the order instituting the investigation was issued. The commission shall consolidate the hearing on the investigation with the next general rate proceeding instituted for the corporation.
(d) Upon being informed by the corporation that any portion of its electric, gas, heat, or water generation or production facility which was eliminated from consideration by the commission in establishing rates for being out of service for nine or more consecutive months pursuant to subdivision (a) or (b), has been restored to service and has achieved at least 100 continuous hours of operation, the commission may again consider that portion of the facility for purposes of establishing rates, and may adjust the corporation’s rates accordingly without a hearing, except that a hearing is required on whether to include, for purposes of establishing rates, any additional plant value added.
(e) Nothing in this section prohibits the commission from reviewing the effects of any electric, gas, heat, or water generation or production facility which has been out of service for less than nine consecutive months or planned outages of predetermined duration scheduled in advance.
(f) For purposes of this section, an electric, gas, heat, or water generation or production facility includes only such a facility that the commission determines to be a major facility of the corporation, and does not include any facility determined by the commission to constitute a plant held for future use.