Ind. Code § 8-1-2-34.5
(a) The Commission shall establish reasonable rules and regulations to govern the relations between public utilities and any or all classes of their customers. Those rules and regulations shall cover the following subjects:
(c) This section does not invalidate any rule or regulation adopted by the commission before July 1, 1979, to govern the relations between public utilities and their consumers if the rule or regulation is consistent with this section.
As added by Acts 1979, P.L.85, SEC.2.