§ 132. Contract to provide for reduction of price. Every such contract shall also provide and require that during the term therein specified the corporation party thereto may and shall supply gas to the inhabitants of such city at prices lower than those now or then charged therein by such corporation party thereto and progressively lower for each year of such term; any company or corporation bidding for such contract shall specify such several prices and reductions of price for the several classes and terms of gas supply, and the same shall be considered in the award of any such contract to the bidders or bidder therefor, and the corporation receiving any such contract shall be entitled to charge and collect the prices therein specified during the continuance thereof. Nothing in this article contained is intended or shall be construed to affect or impair any existing right or contract except with the consent of the parties to any such contract.