Sec. 7. The total capacity of the batteries contained within a single enclosure in:
(1) a utility scale battery energy storage system installation of which is subject to department approval under section 4(a)(1) of this chapter; or
(2) an installation added to an existing utility scale battery energy storage system in an expansion for which department approval is required under section 4(a)(2) of this chapter;
may not exceed ten (10) megawatt hours unless authorized under rules adopted by the commission under this chapter.