WECC expects two regions to be under elevated risk as the West heads into the winter, with staff saying a prolonged weather event could impact operating reserves.

Speaking at a Nov. 4 WECC webinar about the organization’s upcoming 2025 winter reliability assessment, Matt Zapotocky, senior reliability assessments engineer, said the Northwest and Basin regions are at elevated risk — meaning there is potential for insufficient operating reserves in case of an extreme cold weather event coinciding with elevated demand or a significant reduction in resources.

The two regions cover Oregon, Washington, Idaho, Montana, Utah and western Wyoming.

A prolonged cold weather event in those areas could lead to “power not being available and the inability to maintain their operating reserves, and that’s why they were suggested as elevated this year in the assessment,” Zapotocky said. “However, it should be noted that neither area should have lost load for the upcoming winter, assuming there is import availability for both regions.”

James Hanson, manager of operations analysis at WECC, said a major concern is the impact of cold weather events on warmer regions, as seen in January 2024 during Winter Storm Heather.

“There were some significant challenges that parts of the interconnection were facing during that time,” Hanson said. “We fared relatively well. I think … readiness plans, making sure critical components on your power plants are able to withstand those extreme colds, I think that really boded well for a lot of our generation.”

Still, if cold weather extends into a more temperate area “like the Desert Southwest, we could see some operating challenges for sure,” Hanson said.

The resource mix also plays a role in the winter assessment. The West is expected to see approximately 4 GW of coal retirements in 2025, along with about 1 GW of planned natural gas retirements. However, some of the natural gas retirements will be offset by natural gas additions projected to come online in January 2026, Zapotocky said.

Those resources are valuable in the winter and can effectively address unplanned and forced outages, he added.

Though the West will see about 11 GW of solar and 7 GW of wind added across the Western Interconnection, inverter-based resources are more at risk during cold weather events, Zapotocky noted.

“Wind turbines can be susceptible to icing or cold weather cutouts, or even overspeed if the winds are strong enough,” Zapotocky said. “Solar capability can either just not be available if it’s a morning peak and it’s still dark out or just be severely limited due to snow or cloud coverage.”

WECC anticipates over 10 GW of battery energy storage coming online this winter, but those systems can only “provide about four hours of discharge,” Zapotocky said.

“So if you have a prolonged weather event, that may not be enough to quite get you through it,” he added. “There have to be strategies to stagger their use.”

The additional capacity of wind, solar and batteries will be of “particular importance” to the Northwest as the region is forecasting a winter peak 9% higher than last year’s forecast, according to Zapotocky.

WECC will publish the full winter reliability assessment Nov. 13.