If the Commission rules and issues its order within the time aforesaid, and the utility shall appeal from the order, by filing with the Commission a petition for rehearing, the utility may put the rates requested in its schedule into effect under bond only during the appeal and until final disposition of the case. Such bond must be in a reasonable amount approved by the Commission, with sureties approved by the Commission, conditioned upon the refund, in a manner to be prescribed by order of the Commission, to the persons, corporations, or municipalities, respectively, entitled to the amount of the excess, if the rate or rates put into effect are finally determined to be excessive; or there may be substituted for the bond other arrangements satisfactory to the Commission for the protection of parties interested. During any period in which a utility shall charge increased rates under bond, it shall provide records or other evidence of payments made by its subscribers or patrons under the rate or rates which the utility has put into operation in excess of the rate or rates in effect immediately prior to the filing of the schedule.
All increases in rates put into effect under the provisions of this section which are not approved and for which a refund is required shall bear interest at a rate of twelve percent per annum.
The interest shall commence on the date the disallowed increase is paid and continue until the date the refund is made.
In all cases in which a refund is due, the Commission shall order a total refund of the difference between the amount collected under bond and the amount finally approved.
S.C. Code § 58-5-240