Mass. Gen. Laws ch. 164 § 94
Electric companies shall file with the department schedules, not less frequently than every 5 years, and gas companies shall file with the department schedules, not less frequently than every 10 years, under a filing schedule as prescribed by the department and in such form as the department shall prescribe, showing all rates, prices and charges to be charged or collected within the commonwealth for the sale and distribution of gas or electricity, together with all forms of contracts to be used in connection with such schedules; provided, however, that the requirement to file a schedule with the department not less frequently than every 5 or 10 years shall not apply to a company or corporation as defined in section 1 of chapter 165. Rates, prices and charges in such a schedule may be changed by any such company by filing a schedule setting forth the changed rates, prices and charges; provided, however, that until the effective date of any such change no different rate, price or charge shall be charged, received or collected by the company filing such a schedule from those specified in the schedule then in effect; provided, further, that a company may: (i) continue to charge, receive and collect rates, prices and charges under a contract lawfully entered into before the schedule takes effect or until the department otherwise orders, after notice to the company, a public hearing and makes a determination that the public interest so requires; and (ii) sell and distribute gas or electricity under a special contract hereafter made at rates or prices differing from those contained in a schedule in effect; provided, further, that a copy of the contract, in each instance, shall be filed with the department, except that a contract of a company whose sole business in the commonwealth is the supply of electricity in bulk need not file, except as may be required by the department.
If the department receives notice of any changes proposed to be made in any schedule filed under this chapter which represent a general increase in rates, prices and charges for gas or electric service, it shall notify the attorney general immediately and shall hold a public hearing and make an investigation as to the propriety of such proposed changes after first causing notice of the time, place and the subject matter of such hearing to be published at least 21 days before such hearing in such local newspapers as the department may select. Unless the department otherwise authorizes, the rates, prices and charges under the schedule of a gas or electric company shall not become effective until the first day of the month next after the expiration of 14 days from the filing of the petition; provided, that the department shall not authorize rates filed by an electric company under a proposed settlement agreement more than once in a 10-year period. Unless the department otherwise authorizes, the rates, prices and charges set forth in the schedule of a corporation or company, as defined in said section 1 of said chapter 165, shall not become effective until the first day of the month next after the expiration of 14 days from the filing of the petition. Such rates, prices and charges shall apply to the consumption shown by meter readings made after the effective date of such rates, prices and charges, unless the department otherwise orders. So much of said schedules shall be printed in such form and distributed and published in such manner as the department may require.
The department, either upon complaint or upon its own motion, may investigate the propriety of any proposed rate, price or charge and may, pending such investigation and decision thereon by order served upon the company affected thereby, suspend the taking effect thereof, from time to time, but not for a period longer than ten months beyond the time when such rate, price or charge would otherwise become effective. An order by the department directing a change in any schedule filed shall have the same effect as if a schedule with such changes were filed by the company, and shall become effective from such time as the department shall order.
Unless the department otherwise orders, all contracts for the sale of gas or electricity by gas or electric companies, except contracts for sale by a company whose sole business in this commonwealth is the supply of electricity in bulk, shall be filed with the department and shall not become effective until thirty days after filing. The department may investigate the propriety of any such contract, both before and after such contract has become effective, and may, after notice and a public hearing, make such order relative to the rates, prices, charges and practices covered by such contract as the public interest requires. Any order made under the provisions of this section or of section ninety-three, may be enforced as provided in section seventy-nine. This section shall not apply to contracts for the sale of electricity to an electric company made in accordance with the provisions of section ninety-four A except as therein provided. Generation companies and suppliers shall be exempt from the provisions of this section.
Mass. Gen. Laws ch. 164, § 94