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4 requirements did not eliminate these risks. Ibid. EPA concluded that “costs should not be considered” when deciding whether power plants should be regulated under §7412. Id., at 9326.

In accordance with Executive Order, the Agency issued a “Regulatory Impact Analysis” alongside its regulation. This analysis estimated that the regulation would force power plants to bear costs of $9.6 billion per year. Id., at 9306. The Agency could not fully quantify the benefits of reducing power plants’ emissions of hazardous air pollutants; to the extent it could, it estimated that these benefits were worth $4 to $6 million per year. Ibid. The costs to power plants were thus between 1,600 and 2,400 times as great as the quantifiable benefits from reduced emissions of hazardous air pollutants. The Agency continued that its regulations would have ancillary benefits— including cutting power plants’ emissions of particulate matter and sulfur dioxide, substances that are not covered by the hazardous-air-pollutants program. Although the Agency’s appropriate-and-necessary finding did not rest on these ancillary effects, id., at 9320, the regulatory impact analysis took them into account, increasing the Agency’s estimate of the quantifiable benefits of its regulation to $37 to $90 billion per year, id., at 9306. EPA concedes that the regulatory impact analysis “played no role” in its appropriate-and-necessary finding. Brief for Federal Respondents 14.

Petitioners (who include 23 States) sought review of EPA’s rule in the Court of Appeals for the D. C. Circuit. As relevant here, they challenged the Agency’s refusal to consider cost when deciding whether to regulate power plants. The Court of Appeals upheld the Agency’s decision not to consider cost, with Judge Kavanaugh concurring in part and dissenting in part. White Stallion Energy Center, LLC v. EPA, 748 F. 3d 1222 (2014) (per curiam). We granted certiorari. 574 U. S. ___ (2014).