(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.