(a) No public service company may charge rates in excess of those previously approved by the Public Utilities Control Authority or the Public Utilities Regulatory Authority, except that any rate approved by the Public Utilities Commission, the Public Utilities Control Authority or the Public Utilities Regulatory Authority shall be permitted until amended by the Public Utilities Regulatory Authority, that rates not approved by the Public Utilities Regulatory Authority may be charged pursuant to subsection (b) of this section, and that the hearing requirements with respect to adjustment clauses are as set forth in § 16-19b. For water companies, existing rates shall include the amount of any adjustments approved pursuant to § 16-262w since the company’s most recent general rate case, provided any adjustment amount shall be separately identified in any customer bill. Each public service company shall file any proposed amendment of its existing rates with the authority in such form and in accordance with such reasonable regulations as the authority may prescribe. Each electric distribution, gas or telephone company filing a proposed amendment shall also file with the authority an estimate of the effects of the amendment, for various levels of consumption, on the household budgets of high and moderate income customers and customers having household incomes not more than one hundred fifty per cent of the federal poverty level. Each electric distribution company shall also file such an estimate for space heating customers. Each water company, except a water company that provides water to its customers less than six consecutive months in a calendar year, filing a proposed amendment, shall also file with the authority a plan for promoting water conservation by customers in such form and in accordance with a memorandum of understanding entered into by the authority pursuant to § 4-67e. Each public service company shall notify each customer who would be affected by the proposed amendment, by mail, at least one week prior to the first public hearing thereon, but not earlier than six weeks prior to such first public hearing, that an amendment has been or will be requested. Such notice shall also indicate (1) the date, time and location of any scheduled public hearing, (2) a statement that customers may provide written comments regarding the proposed amendment to the Public Utilities Regulatory Authority or appear in person at any scheduled public hearing, (3) the Public Utilities Regulatory Authority telephone number for obtaining information concerning the schedule for public hearings on the proposed amendment, and (4) whether the proposed amendment would, in the company’s best estimate, increase any rate or charge by twenty per cent or more, and, if so, describe in general terms any such rate or charge and the amount of the proposed increase, provided no such company shall be required to provide more than one form of the notice to each class of its customers. In the case of a proposed amendment to the rates of any public service company, the authority shall hold one or more public hearings thereon, except as permitted with respect to interim rate amendments by subsections (d) and (g) of this section, and shall make such investigation of such proposed amendment of rates as is necessary to determine whether such rates conform to the principles and guidelines set forth in § 16-19e, or are unreasonably discriminatory or more or less than just, reasonable and adequate, or that the service furnished by such company is inadequate to or in excess of public necessity and convenience, provided the authority may (A) evaluate the reasonableness and adequacy of the performance or service of the public service company using any applicable metrics or standards adopted by the authority pursuant to § 16-244aa, and (B) determine the reasonableness of the allowed rate of return of the public service company based on such performance evaluation. The authority, if in its opinion such action appears necessary or suitable in the public interest may, and, upon written petition or complaint of the state, under direction of the Governor, shall, make the aforesaid investigation of any such proposed amendment which does not involve an alteration in rates. If the authority finds any proposed amendment of rates to not conform to the principles and guidelines set forth in § 16-19e, or to be unreasonably discriminatory or more or less than just, reasonable and adequate to enable such company to provide properly for the public convenience, necessity and welfare, or the service to be inadequate or excessive, it shall determine and prescribe, as appropriate, an adequate service to be furnished or just and reasonable maximum rates and charges to be made by such company. In the case of a proposed amendment filed by an electric distribution, gas or telephone company, the authority shall also adjust the estimate filed under this subsection of the effects of the amendment on the household budgets of the company’s customers, in accordance with the rates and charges approved by the authority. The authority shall issue a final decision on each electric distribution or gas company rate filing within three hundred fifty days from the proposed effective date thereof. The authority shall issue a final decision on all public service company rate filings, except electric distribution or gas company rate filings, within two hundred days from the proposed effective date thereof.

(b) If the authority has not made its finding respecting an amendment of any electric distribution or gas company rate within three hundred fifty days from the proposed effective date of such amendment thereof, or if the authority has not made its finding respecting an amendment of any public service company rate, except an electric distribution or a gas company rate, within two hundred days from the proposed effective date of such amendment thereof, such amendment may become effective pending the authority’s finding with respect to such amendment upon the filing by the company with the authority of assurance satisfactory to the authority, which may include a bond with surety, of the company’s ability and willingness to refund to its customers with interest such amounts as the company may collect from them in excess of the rates fixed by the authority in its finding or fixed at the conclusion of any appeal taken as a result of a finding by the authority.

(c) Upon conclusion of its investigation of the reasonableness of any proposed increase of rates, the authority shall order the company to refund to its customers with interest any amounts the company may have collected from them during the period that any amendment permitted by subsection (b) of this section was in force, which amounts the authority may find to have been in excess of the rates fixed by the authority in its finding or fixed at the conclusion of any appeal taken as a result of a finding by the authority. Any such refund ordered by the authority shall be paid by the company, under direction of the authority, to its customers in such amounts as are determined by the authority.

(d) Nothing in this section shall be construed to prevent the authority from approving an interim rate increase, if the authority finds that such an interim rate increase is necessary to prevent substantial and material deterioration of the financial condition of a public service company, to prevent substantial deterioration of the adequacy and reliability of service to its customers or to conform to the applicable principles and guidelines set forth in § 16-19e, provided the authority shall first hold a special public hearing on the need for such interim rate increase and the company, at least one week prior to such hearing, notifies each customer who would be affected by the interim rate increase that such an increase is being requested. The company shall include the notice in a mailing of customer bills, unless such a mailing would not provide timely notice, in which case the authority shall authorize an alternative manner of providing such notice. Any such interim rate increase shall only be permitted if the public service company submits an assurance satisfactory to the authority, which may include a bond with surety, of the company’s ability and willingness to refund to its customers with interest such amounts as the company may collect from such interim rates in excess of the rates approved by the authority in accordance with subsection (a) of this section. The authority shall order a refund in an amount equal to the excess, if any, of the amount collected pursuant to the interim rates over the amount which would have been collected pursuant to the rates finally approved by the authority in accordance with subsection (a) of this section or fixed at the conclusion of any appeal taken as a result of any finding by the authority. Such refund ordered by the authority shall be paid by the company to its customers in such amounts and by such procedure as ordered by the authority.

(e) If the authority finds that the imposition of any increase in rates would create a hardship for a municipality, because such increase is not reflected in its then current budget, or cannot be included in the budget of its fiscal year which begins less than five months after the effective date of such increase, the authority may defer the applicability of such increase with respect to services furnished to such municipality until the fiscal year of such municipality beginning not less than five months following the effective date of such increase; provided the revenues lost to the public service company through such deferral shall be paid to the public service company by the municipality in its first fiscal year following the period of such deferral.

(f) Any public service company, as defined in § 16-1, filing an application with the Public Utilities Regulatory Authority to reopen a rate proceeding under this section, which application proposes to increase the company’s revenues or any rate or charge of the company by five per cent or more, shall, not later than one week prior to the hearing under the reopened proceeding, notify each customer who would be affected thereby that such an application is being filed. Such notice shall indicate the rate increases proposed in the application. The company shall include the notice in a mailing of customer bills, unless such a mailing would not provide timely notice to customers of the reopening of the proceeding, in which case the authority shall authorize an alternative manner of providing such notice.

(g) The authority shall hold either a special public hearing or combine an investigation with an ongoing four-year review conducted in accordance with § 16-19a or with a general rate hearing conducted in accordance with subsection (a) of this section on the need for an interim rate decrease (1) when a public service company has, for the rolling twelve-month period ending with the two most recent consecutive financial quarters, earned a return on equity which exceeds the return authorized by the authority by at least one percentage point, (2) if it finds that any change in municipal, state or federal tax law creates a significant increase in a company’s rate of return, or (3) if it finds that a public service company may be collecting rates which are more than just, reasonable and adequate, as determined by the authority, provided the authority shall require appropriate notice of hearing to the company and its customers who would be affected by an interim rate decrease in such form as the authority deems reasonable. The company shall be required to demonstrate to the satisfaction of the authority that earning such a return on equity or collecting rates which are more than just, reasonable and adequate is directly beneficial to its customers. At the completion of the proceeding, the authority may order an interim rate decrease if it finds that such return on equity or rates exceeds a reasonable rate of return or is more than just, reasonable and adequate as determined by the authority. Any such interim rate decrease shall be subject to a customer surcharge if the interim rates collected by the company are less than the rates finally approved by the authority or fixed at the conclusion of any appeal taken as a result of any finding by the authority. Such surcharge shall be assessed against customers in such amounts and by such procedure as ordered by the authority.

(h) The provisions of this section shall not apply to the regulation of a telecommunications service which is a competitive service, as defined in § 16-247a, or to a telecommunications service to which an approved plan for an alternative form of regulation applies, pursuant to § 16-247k.