Tex. Util. Code § 39.454
An electric utility subject to this subchapter is entitled to recover, as provided by this section, all reasonable and necessary expenditures made or incurred before the effective date of this section to comply with this chapter, to the extent the costs have not otherwise been recovered. The electric utility may file with the commission an application for recovery that gives details of the amounts spent or incurred. After notice and hearing, the commission shall review the amounts and, if the amounts are found to be reasonable and necessary and not otherwise previously recovered, approve a transition to competition retail rate rider mechanism for the recovery of the approved transition to competition costs. A rate proceeding under Chapter 36 is not required to implement the rider. A rate rider implemented to recover approved transition to competition costs shall provide for recovery of those costs over a period not to exceed 15 years, with appropriate carrying costs.
Tex. Util. Code § 39.454