66 Pa.C.S. § 513

Whenever the commission deems that the public interest so requires, it may direct, by regulation or order, that any public utility shall award contracts or agreements for the construction, improvement, or extension, of its plant or system to the lowest responsible bidder, after a public offering has been made, after advertisement and notice. Any such public utility may participate as a bidder in any such public offering. The commission may prescribe regulations relative to such advertisement, notice, and public letting.