(a) No public utility shall require any deposit of any residential customer which shall exceed one twelfth of the estimated annual charge to the customer for such service: Provided, That the provisions of this section shall not apply to deposits received prior to March 12, 1983.
(b) Public utilities may collect and hold a security deposit in accordance with this statute and the rules established by the commission. No interest shall be payable on security deposits when a deposit is, no later than 30 days following the date of the end of the eighteenth month of service, either (1) applied as a credit to the customer’s account, or (2) returned or refunded to the customer by some other means.