No State, or political subdivision thereof, may impose or assess a tax on or with respect to the generation or transmission of electricity which discriminates against out-of-State manufacturers, producers, wholesalers, retailers, or consumers of that electricity. For purposes of this section a tax is discriminatory if it results, either directly or indirectly, in a greater tax burden on electricity which is generated and transmitted in interstate commerce than on electricity which is generated and transmitted in intrastate commerce. ( Pub. L. 86–272, title II, § 201 , as added Pub. L. 94–455, title XXI, § 2121(a) , Oct. 4, 1976 , 90 Stat. 1914 .) Statutory Notes and Related Subsidiaries Effective Date Pub. L. 94–455, title XXI, § 2121(b) , Oct. 4, 1976 , 90 Stat. 1914 , provided that: “The amendment made by subsection (a) [enacting this section] shall take effect beginning June 30, 1974 .”