(a) In addition to any tax imposed under § 11-102 of this title, except as provided in subsection (b) of this section, a tax is imposed on the use, in the State, of electricity that is not delivered by a public service company.
(b) The special use tax on electricity does not apply to the use of:
(1) electricity that is:
(i) used for residential purposes; or
(ii) used exclusively for emergency back-up generation; or
(2) on-site generated electricity.