Tex. Utilities Code § 39.455

An electric utility subject to this subchapter is entitled to recover, through a rate rider mechanism, reasonable and necessary costs of incremental resources required to meet load requirements to the extent those costs result in the utility expending more for capacity costs under purchase power agreements than were included in the utility's last base rate case, adjusted for load growth. Any rider under this section shall be implemented after review and approval by the commission, after notice and opportunity for hearing. Following the initial implementation of the rider, an electric utility subject to this subchapter may request revisions semiannually, after notice and opportunity for hearing, on the dates provided in the commission's rules for filing petitions to revise the utility's fuel factor. In conjunction with the utility's fuel reconciliation proceedings, the commission shall reconcile the costs recovered under the rider and the actual incremental capacity costs eligible for recovery under this section. The rider shall expire on the introduction of customer choice or on the implementation of rates resulting from the filing of a Subchapter C, Chapter 36, rate proceeding. In no event may the amount recovered annually under the rider exceed five percent of the utility's annual base rate revenues.