Searing summer heat is stressing Public Service Company of New Mexico’s grid as consumers blast their air conditioners, but a utility decision to partially postpone closure of the coal-fired San Juan Generating Station makes blackouts unlikely.

Electricity consumption in PNM’s service territory hit record levels early this week as triple-digit temperatures engulfed New Mexico and many other states.

“Peak load,” or maximum daily consumer electric demand, climbed to all-time highs on Monday and Tuesday, said PNM Vice President for Generation Tom Fallgren.

“We set a record on Monday, and then a new record on Tuesday,” Fallgren told the Journal. “Our previous record was in 2013, when demand hit 2,008 megawatts. But early this week, that climbed by about 3% more, or about 60 MW higher than during the 2013 peak.”

Peak summer load usually occurs at 5 p.m., after sidewalks, pavement and other ground-based structures absorb hours of penetrating daytime solar heat that then radiates back into the environment, raising temperatures even more just as most consumers return home from work or other activities and collectively blast their air conditioners.

Peak load reached 2,043 MW Monday afternoon. And at 5 p.m. Tuesday, it climbed to 2,069 MW, Fallgren said.

At those levels, PNM must cut into its “reserve margin” of power, which refers to additional internal electric generation available on the utility grid to meet spikes in demand that climb beyond normal anticipated load. Rolling blackouts happen when peak load surpasses all local available generation and not enough electricity is accessible on regional wholesale markets to cover the extra demand stressing the grid.

That, however, didn’t happen this week, because PNM decided last February to partially postpone the permanent shutdown of the San Juan coal plant, which it had previously planned to do on June 30 as part of utility efforts to transition the grid from fossil fuels to renewable energy. The company did close one of the plant’s two operating units on June 30, but the last remaining unit is still functioning, and will remain in operation until Sept. 30.

Shutdown postponement was necessary because pandemic-related supply-chain problems and regulatory issues delayed construction of four new solar plants slated to replace San Juan. Those facilities now won’t come online until late 2022 and early 2023.

“The San Juan unit has continued to perform well, so we had few challenges during this week’s peaks,” Fallgren said. “It put us in a good position to ensure grid reliability.”

In addition, excess power from hydroelectric plants in the Pacific Northwest and Canada is available on the wholesale market if the current heat wave intensifies, or pushes PNM’s peak load beyond reserve margins, said PNM spokesman Ray Sandoval.

“We’re not too concerned about that, but we’re monitoring it closely,” Sandoval told the Journal.

Still, while San Juan’s continued operation will likely avoid any blackouts this summer, PNM could face major challenges in summer 2023. That’s because the utility will lose 104 MW of power that it currently receives from the Palo Verde Nuclear Generating Station in Arizona after one of its leases in that plant expires in January.

Like the San Juan replacement power, supply-chain and regulatory issues have also delayed construction of additional solar facilities slated to replace Palo Verde electricity until at least year-end 2023. And with San Juan completely shutting down this fall, PNM will need to find alternative power supplies to navigate next summer’s peak loads.