66 Pa.C.S. § 1309

(a) General rule.--Whenever the commission, after reasonable notice and hearing, upon its own motion or upon complaint, finds that the existing rates of any public utility for any service are unjust, unreasonable, or in anywise in violation of any provision of law, the commission shall determine the just and reasonable rates, including maximum or minimum rates, to be thereafter observed and in force, and shall fix the same by order to be served upon the public utility, and such rates shall constitute the legal rates of the public utility until changed as provided in this part. Whenever a public utility does not itself produce or generate that which it distributes, transmits, or furnishes to the public for compensation, but obtains the same from another source, the commission shall have the power and authority to investigate the cost of such production or generation in any investigation of the reasonableness of the rates of such public utility.

(b) Deadline for decision.--Before the expiration of a nine-month period beginning on the date of the commission's motion or the filing of a complaint pursuant to subsection (a), a majority of the members of the commission serving in accordance with law, acting unanimously, shall make a final decision and order, setting forth its reasons therefor. If such an order has not been made at the expiration of such nine-month period and the motion or complaint pursuant to subsection (a) requested a reduction in rates, a final decision and order of the commission which determines or fixes a rate reduction shall be retroactive to the expiration of such nine-month period, provided that nothing herein shall be construed to prohibit the commission from setting temporary rates pursuant to section 1310 (relating to temporary rates) prior to the expiration of such nine-month period and giving such effect to the setting of temporary rates as is otherwise permitted by this title. This subsection shall apply only when the requested reduction in rates affects more than 5% of the customers and amounts to in excess of 3% of the total gross annual intrastate operating revenues of the public utility, provided that, if the public utility furnishes two or more types of service, the foregoing percentages shall be determined only on the basis of the customers receiving, and the revenues derived from, the type of service to which the requested reduction pertains. This subsection shall not apply to any proceeding involving a change in rates proposed by a public utility pursuant to section 1307 (relating to sliding scale of rates; adjustments) or 1308 (relating to voluntary changes in rates). (July 6, 1988, P.L.490, No.83, eff. imd.) Cross References. Section 1309 is referred to in sections 514, 521, 1327, 3019 of this title.