Mass. Gen. Laws ch. 164 § 93
On written complaint of the attorney general, of the mayor of a city or the selectmen of a town where a gas or electric company is operated, or of twenty customers thereof, either as to the quality or price of the gas or electricity sold and delivered, the department shall notify said company by leaving at its office a copy of such complaint, and shall thereupon, after notice, give a public hearing to such complainant and said company, and after such hearing may order any reduction or change in the price or prices of gas or electricity or an improvement in the quality thereof, and a report of such proceedings and the result thereof shall be included in the report required by section seventy-seven. Such an order may likewise be made by the department, after notice and hearing as aforesaid, upon its own motion. The price or prices fixed by any such order shall not thereafter be changed by said company except as provided in section ninety-four.
Mass. Gen. Laws ch. 164, § 93