66 Pa. C.S. § 1315
Except for such nonrevenue producing, nonexpense reducing investments as may be reasonably shown to be necessary to improve environmental conditions at existing facilities or improve safety at existing facilities or as may be required to convert facilities to the utilization of coal, the cost of construction or expansion of a facility undertaken by a public utility producing, generating, transmitting, distributing or furnishing electricity shall not be made a part of the rate base nor otherwise included in the rates charged by the electric utility until such time as the facility is used and useful in service to the public. Except as stated in this section, no electric utility property shall be deemed used and useful until it is presently providing actual utility service to the customers.
66 Pa.C.S. § 1315