(a) Temporary or permanent rates set by the commission are prospective and observed from the date of the applicable commission order, except an interim rate order necessary to effect uniform system-wide rates or to provide an electric utility the opportunity to avoid confiscation during the period beginning on the date a petition for review is filed with the commission and ending on the date of a final order establishing rates.(b) The commission shall order interim rates on a prima facie showing by the electric utility that it has experienced confiscation during that period. The electric utility shall refund or credit against future bills:(1) money collected under the interim rates in excess of the rate finally ordered; and(2) interest on that money, at the current rate as determined by the commission.(c) In this section, 'confiscation' includes negative cash flow experienced by an electric utility at any time a rate case proceeding is pending. Acts 1997, 75th Leg., ch. 166, Sec. 1, eff. Sept. 1, 1997.