The New York Public Service Commission on Monday petitioned the D.C. Circuit Court of Appeals to review FERC’s approval of NYISO’s proposal to use a 17-year amortization period in capacity auction demand curves (ER21-502).

NYISO proposed to move from a 20-year amortization period — the assumed time that a hypothetical peaking plant is expected to be operational — to 17 years in response to state legislation that set strict net-zero requirements that are forcing fossil plants to retire sooner.

After rejecting it twice previously, FERC accepted the ISO’s proposal in May on remand from the D.C. Circuit. (See FERC Accepts NYISO’s 17-Year Amortization Period Proposal.) The commission’s rejection had been challenged by the Independent Power Producers of New York.

“The unjustified shortening of the amortization period will needlessly increase capacity auction charges by hundreds of millions of dollars,” the PSC said. The commission’s decision “must be reversed because it fails to provide the requisite ‘reasoned analysis.’”

The ISO’s revisions were part of a suite of changes called the demand curve reset, which altered the assumptions and scope for capability years 2021/22 through 2024/25 to predict the volume of megawatts needed to meet demand.