The Government attempts to downplay the magnitude of this “unprecedented power over American industry.” Industrial Union Dept., AFL–CIO v. American Petroleum Institute, 448 U. S. 607, 645 (1980) (plurality opinion). The amount of generation shifting ordered, it argues, must be “adequately demonstrated” and “best” in light of the statu tory factors of “cost,” “nonair quality health and environmental impact,” and “energy requirements.” 42 U. S. C. §7411(a)(1). EPA therefore must limit the magnitude of generation shift it demands to a level that will not be “exorbitantly costly” or “threaten the reliability of the grid.” Brief for Federal Respondents 42. But this argument does not so much limit the breadth of the Government’s claimed authority as reveal it. On EPA’s view of Section 111(d), Congress implicitly tasked it, and it alone, with balancing the many vital considerations of national policy implicated in deciding how Americans will get their energy. EPA decides, for instance, how much of a switch from coal to natural gas is practically feasible by 2020, 2025, and 2030 before the grid collapses, and how high energy prices can go as a result before they become unreasonably “exorbitant.”
There is little reason to think Congress assigned such decisions to the Agency.