BTW, the language in the decision never uses the term "grid level," so I don't know what the hell you are talking about.
From the Syllabus:
Building blocks two and three were quite different, as both involved what EPA called “generation shifting” at the grid level—i.e., a shift in electricity production from higher-emitting to lower-emitting producers.
EPA explained that the Clean Power Plan, rather than setting the standard “based on the application of equipment and practices at the level of an individual facility,” had instead based it on “a shift in the energy generation mix at the grid level,” id., at 32523.
Indeed, the Agency nodded to the novelty of its approach when it explained that it was pursuing a “broader, forward-thinking approach to the design” of Section 111 regulations that would “improve the overall power system,” rather than the emissions performance of individual sources, by forcing a shift throughout the power grid from one type of energy source to another. 80 Fed. Reg. 64703 (emphasis added). This view of EPA’s authority was not only unprecedented; it also effected a “fundamental revision of the statute, changing it from [one sort of] scheme of . . . regulation” into an entirely different kind.
The Government attempts to downplay matters, noting that the Agency 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.”
From the Opinion of the Court:
EPA explained that taking any of these steps would implement a sector-wide shift in electricity production from coal to natural gas and renewables. Id., at 64731. Given the integrated nature of the power grid, “adding electricity to the grid from one generator will result in the instantaneous reduction in generation from other generators,” and “reductions in generation from one generator lead to the instantaneous increase in generation” by others.
It then explained that the Clean Power Plan, rather than setting the standard “based on the application of equipment and practices at the level of an individual facility,” had instead based it on “a shift in the energy generation mix at the grid level,” id., at 32523—not the sort of measure that has “a potential for application to an individual source.” Id., at 32524.
And it would do that by forcing a shift throughout the power grid from one type of energy source to another.
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.”
From the Dissenting Opinion:
That result follows because regulations affect costs, and the electrical grid works by taking up energy from low-cost providers before high-cost ones.
That action increases those plants’ costs, and automatically (by virtue of the way the grid operates) reduces their share of the electricity market.
If you had taken the time to just read the ******* opinions, you wouldn't get embarrassed like this.