66 Pa.C.S. § 1301: Rates to be just and reasonable.

(a) Regulation.--Every rate made, demanded, or received by any public utility, or by any two or more public utilities jointly, shall be just and reasonable, and in conformity with regulations or orders of the commission. Only public utility service being furnished or rendered by a municipal corporation, or by the operating agencies of any municipal corporation, beyond its corporate limits, shall be subject to regulation and control by the commission as to rates, with the same force, and in like manner, as if such service were rendered by a public utility.

(b) Municipal corporations.--In determining a just and reasonable rate furnished or rendered by a municipal corporation or by the operating agencies of a municipal corporation providing public utility water or wastewater service beyond its corporate limits, the commission shall employ an imputed capital structure of comparable public utilities providing water or wastewater service.