The commission may, after a preliminary investigation by the Office of Regulatory Staff and upon such evidence as to the commission seems sufficient, order any electrical utility to put into effect a schedule of rates as shall be deemed fair and reasonable, within such time as may be prescribed by order of the commission, which shall be not less than fifteen days, and an attested copy of the order must be served upon the utility and the Office of Regulatory Staff by registered mail or otherwise as provided by law.
S.C. Code § 58-27-920