66 Pa.C.S. § 1305

No public utility shall require the payment of rates in advance, or the making of minimum payments, ready to serve charges, or deposits to secure future payments of rates, except as the commission, by regulation or order, may permit. Any deposit made by any domestic consumer, under the provisions of this section or under any repealed statute supplied by this part, shall be returned with any interest due thereon to the consumer making such deposit when he shall have paid undisputed bills for service over a period of 12 consecutive months.