(a) The Arkansas Public Service Commission is hereby empowered, following notice and hearing, to order any public utility subject to its jurisdiction to make refunds. The refunds shall be made in the manner and to the extent determined just and reasonable by the commission.
(b) The authority of the commission to make refunds shall include, but is not limited to, the following circumstances:
(1) When a utility implements rates under bond, and the rates approved in the final order of the commission are less than the bonded rates;
(2) When a utility has charged its ratepayers an amount in excess of the utility's approved tariffs;
(3) When a utility imposes on ratepayers any charge prohibited by, or in excess of, any Arkansas statute;
(4) When a utility charges more than the lawful rate of interest; and
(5) When a utility has collected revenues exceeding those amounts authorized by any contract approved by the commission pursuant to § 23-3-117.
(c) When the commission determines that refunds are due under this section, the commission may authorize the utility to make a refund in one (1) lump sum, or may authorize the utility to prorate the refunds over the period of time over which the amount to be refunded had accrued, or some intermediate period of time as the commission deems appropriate. The commission may require that the refund be made by cash or check, or through customers' account credits. However, any refund of ten dollars ($10.00) or less shall be by billing credit only. All refunds, of whatever amount, to customers who cannot be located shall be made pursuant to subsection (e) of this section. Former customers who can be located shall be paid by cash or check.
(d) The commission may order that refunds due under this section be made with interest computed at a rate not to exceed the maximum allowed by Arkansas law.
(e) When a refund is due a customer and the utility cannot, after diligent effort, locate the customer, the utility shall:
(1) Make the refunds available to the customer for a period of three (3) years from the date the refund was ordered; and
(2) Apply those funds which are not claimed after three (3) years as a credit against bad-debt expense of the utility.
(f) Nothing in this section shall be construed as allowing retroactive ratemaking or otherwise providing for refunds of rates collected pursuant to previous orders of the commission, except when rates have been placed in effect under bond, subject to refund.