The New York Public Service Commission on Friday petitioned the D.C. Circuit Court of Appeals to review FERC’s approval of NYISO’s 17-year amortization period in its installed capacity market.

The saga around NYISO’s proposal to shorten the assumed lifetime of a hypothetical peaker plant from 20 to 17 years seemed to be settled after FERC earlier this month reaffirmed its decision to approve it (ER21-502). (See FERC Reaffirms NYISO’s 17-Year Amortization, Dismisses Protests.)

But the PSC’s petition argued the D.C. Circuit should add FERC’s October order to an existing case before the court. The PSC said a comprehensive review by the court of “all aspects of FERC’s decisions” is necessary “to remove any doubt” about the matter (23-1192/23-1259).

NYISO sought the shorter amortization period in response to the state’s strict energy and climate legislative mandates. The PSC says the ISO’s proposal is “unjustified” and will likely increase capacity costs by more than $225 million per year, and $400 million over the 22-month period from July 2023 through April 2025.

NYISO’s proposal was first rejected by FERC, but after the commission’s ruling was appealed by generators, the D.C. Circuit remanded the case back to the commission. FERC reversed course and accepted the ISO’s proposal.

The ISO incorporated its proposals as part of the demand curve reset, a set of adjustments made to help forecast the energy supply needed to meet demand for the upcoming capability years.