Document ID: ./input/supremecourt_opinions/opinions/21pdf/20-1530_n758.pdf
Page Number: 29

Cite as:  597 U. S. ____ (2022) 

23 

Opinion of the Court 

referred to” the “level of control” required as a “best demon-
strated  technology  (BDT)”  standard,  73  Fed.  Reg.  34073, 
and consistently applied it as such.  E.g., 61 Fed. Reg. 9907
(declaring “BDT” to be “a well-designed and well-operated 
gas collection system and . . . a control device capable of re-
ducing  [harmful  gases]  in  the  collected  gas  by  98  weight-
percent.”).

Indeed, EPA nodded to this history in the Clean Power 
Plan itself, describing the sort of “systems of emission re-
duction” it had always before selected—“efficiency improve-
ments,  fuel-switching,”  and  “add-on  controls”—as  “more 
traditional  air  pollution  control  measures.”    80  Fed.  Reg.
64784.  The  Agency  noted  that  it  had  “considered”  such 
measures  as  potential  systems  of  emission  reduction  for 
carbon  dioxide,  ibid.,  including  a  measure  it  ultimately 
adopted as a “component” of the BSER, namely, heat rate
improvements.  Id., at 64727. 

But, the Agency explained, in order to “control[ ] CO2 from 
affected [plants] at levels . . . necessary to mitigate the dan-
gers  presented  by  climate  change,”  it  could  not  base  the 
emissions limit on “measures that improve efficiency at the
power  plants.”  Id.,  at 64728.    “The  quantity  of  emissions 
reductions  resulting 
from  the  application  of  these 
measures” would have been “too small.”  Id., at 64727.  In-
stead,  to  attain  the  necessary  “critical  CO2  reductions,” 
EPA  adopted  what  it  called  a  “broader,  forward-thinking
approach to the design” of Section 111 regulations.  Id., at 
64703.  Rather than focus on improving the performance of
individual sources, it would “improve the overall power sys-
tem by lowering the carbon intensity of power generation.” 
Ibid. (emphasis added).  And it would do that by forcing a
shift  throughout  the  power  grid  from  one  type  of  energy 
source to another.  In the words of the then-EPA Adminis-
trator, the rule was “not about pollution control” so much
as it was “an investment opportunity” for States, especially
“investments in renewables and clean energy.”  Oversight