A Santa Fe-based clean-energy advocacy group claims the state’s largest utility intentionally misled the New Mexico Supreme Court this year about the economics of the aging San Juan Generating Station near Farmington.

In a court filing this week, New Energy Economy says Public Service Company of New Mexico told justices at a January hearing that the company’s plan to replace the generating capacity of two coal-burning units at the San Juan facility with more coal and nuclear power sources was the most cost-effective route.

However, New Energy contends recently discovered documents show that before the court hearing, PNM ran computer analyses that showed this plan would not be cost-effective after 2022. The group says PNM ran the computer analyses in November, December and twice in January prior to oral arguments before the Supreme Court.

“PNM should have informed this court of these developments and that this case should not be decided on the basis of a record in which core evidence, submitted by PNM, either was incorrect when PNM offered it, or has become incorrect as PNM now tacitly concedes,” said New Energy, which is dedicated to weaning the utility off coal in favor of cleaner, renewable power sources such as solar and wind energy.

The state Public Regulation Commission in late 2015 approved a PNM proposal to increase the power output from San Juan’s two remaining coal-fired units, as well as use power from the Palo Verde Nuclear Generating Station in Arizona, natural gas and a small portion of wind and solar sources. New Energy Economy appealed that decision to the Supreme Court.

Since that time, however, the electric company has announced a major shift away from coal power. In April, PNM said it plans to eliminate all reliance on coal power by late 2031 and transition to solar and wind power for nearly a third of its energy mix by 2025.

Mariel Nanasi, executive director of New Energy Economy, said in an email Thursday that New Energy’s “position all along was that coal is no longer cost effective for ratepayers.”

PNM spokesman Dan Ware on Thursday referred a reporter to a letter to the Supreme Court clerk from PNM lawyer Richard Alvidrez that disputes New Energy’s claims about misleading the high court.

“Essentially, the information … [New Energy] is referring to did not exist at the time that the [state Public Regulation Commission] granted approval for the continued operation of the plant,” Ware said, though New Energy argues the information was available before the January court hearing.

PNM’s latest plan calls for shutting the San Juan Generating Station after 2022 and leaving the Four Corners Generating Station in 2031. This, the company now says, is the most cost-effective way forward for the utility and its customers. PNM holds a 13 percent stake in the Four Corners plant.

New Energy said it learned about PNM’s computer analyses in documents it received this week from the utility in a pending rate case before the PRC.

In its court filing, the group also quoted a March 16 news release from PNM that said, “A preliminary analysis by PNM of its options for providing customers energy in the future shows that retiring the remaining two units of San Juan Generating Station … in the Farmington area in 2022 could provide long-term benefits to customers.”

Alvidrez, the PNM lawyer, said in his letter, dated Thursday, that New Energy “is inappropriately asking the court to take additional evidence that was not available, and therefore not before the [Public Regulation] Commission, when it entered the final order that is the subject of the appeal and that has not yet been the subject of hearings before the commission.”

Contrary to New Energy’s filing, Alvidrez said, “PNM at no time represented to the commission or the court that the San Juan Generating Station would remain cost-effective for 20 years and would operate until 2053.”

Contact Steve Terrell at 505-986-3037 or sterrell@sfnewmexica­n.com.