Tex. Utilities Code § 36.065

(a) The regulatory authority shall include in the rates of an electric utility expenses for pension and other postemployment benefits, as determined by actuarial or other similar studies in accordance with generally accepted accounting principles, in an amount the regulatory authority finds reasonable. Expenses for pension and other postemployment benefits include, in an amount found reasonable by the regulatory authority, the benefits attributable to the service of employees who were employed by the predecessor integrated electric utility of an electric utility before the utility's unbundling under Chapter 39 irrespective of the business activity performed by the employee or the affiliate to which the employee was transferred on or after the unbundling.

(b) An electric utility may establish one or more reserve accounts for expenses for pension and other postemployment benefits. An electric utility shall periodically record in the reserve account any difference between:

(1) the annual amount of pension and other postemployment benefits approved as an expense in the electric utility's last general rate proceeding or, if that amount cannot be determined from the regulatory authority's order, the amount recorded for pension and other postemployment benefits under generally accepted accounting principles during the first year that rates from the electric utility's last general rate proceeding are in effect; and

(2) the annual amount of pension and other postemployment benefits as determined by actuarial or other similar studies that are chargeable to the electric utility's expense.

(c) A surplus in the reserve account exists if the amount of pension and other postemployment benefits under Subsection (b)(1) is greater than the amount determined under Subsection (b)(2). A shortage in the reserve account exists if the amount of pension and other postemployment benefits under Subsection (b)(1) is less than the amount determined under Subsection (b)(2).

(d) If a reserve account for pension and other postemployment benefits is established, the regulatory authority at a subsequent general rate proceeding shall:

(1) review the amounts recorded to the reserve account to determine whether the amounts are reasonable expenses;

(2) determine whether the reserve account has a surplus or shortage under Subsection (c); and

(3) subtract any surplus from or add any shortage to the electric utility's rate base with the surplus or shortage amortized over a reasonable time.