(a) Whenever the Commission, after due consideration of pertinent facts and information, is of the opinion that any rates of any public utility are producing a return in excess of a reasonable rate of return upon its rate base, or when appropriate, its operating ratio, and that a proceeding to determine all of the issues involved in a final determination of such rates will require more than 90 days, the Commission may, after reasonable notice to the public utility and opportunity to be heard thereon, if the public interest so requires, immediately enter a temporary order fixing a temporary schedule of rates to be charged by such public utility pending the final determination of such rate proceeding, which order shall become operative and binding upon such public utility at the time prescribed by the Commission.

(b) The power of the Commission to order reductions in rates and charges of any public utility by means of such temporary order shall be limited to reductions which will absorb not more than the amount found to be in excess of the amount of operating income, as determined by the Commission, necessary to provide a reasonable rate of return on the rate base of the public utility or when appropriate, its operating ratio.

(c) The temporary rate so prescribed shall be effective until the final determination of the rate proceeding, unless sooner terminated or changed by the Commission.

(d) If, upon final disposition of the issues involved in such proceeding, the rates as finally determined are in excess of the rates prescribed in such temporary order, then such public utility may amortize and recover by means of a temporary increase over and above the rates finally determined such sum as represents the difference between the operating revenues obtained from the rates prescribed in such temporary order and the operating revenues which would have been obtained under the rates finally determined if applied during the period such temporary order was in effect.

47 Del. Laws, c. 254, § 5A; 48 Del. Laws, c. 371, § 311; 26 Del. C. 1953, § 156; 59 Del. Laws, c. 397, § 1.