America's changing power grid faces a powerful El Niño

A powerful El Niño weather pattern may significantly alter the U.S. power grid's electricity supply and demand this coming winter, presenting new challenges for utilities. The National Oceanic and Atmospheric Administration (NOAA) predicts a very strong El Niño is currently strengthening in the tropical Pacific and is expected to persist into spring 2027.

NOAA forecasts wetter-than-normal conditions across California, the Southwest, and much of the southern United States during the upcoming winter, while the northern Rockies and parts of the Great Lakes are anticipated to be drier, with much of the northern U.S. experiencing warmer temperatures.

The intricate relationship between El Niño and the energy mix is crucial in determining the grid's resilience. A study published in March revealed that previous super El Niños led to nearly a 5% reduction in potential solar power output in certain areas of California over a year, with some regions in the state's north even seeing more than a 10% decrease in winter.

Tidal waves of rain or increased snowpack in California could bolster hydropower generation, while a lack of precipitation or snowpack in the Pacific Northwest might diminish hydropower output there.

Climate scientists, such as Erik Smith of the Electric Power Research Institute, caution that the Southeast may experience reduced solar generation during El Niño due to the region's propensity for cloudier conditions. California boasts more than 21 gigawatts of battery storage capacity, a novel tool that utilities can employ to manage variability in electricity supply.

In the past, the Western grid has demonstrated its ability to redistribute electricity between regions when hydropower conditions fluctuate, helping to mitigate shortages.

Federal water managers, states, and utilities rely on seasonal forecasts to plan for potential hydropower availability at major dams, such as Hoover and Glen Canyon on the Colorado River. Natural gas may step up as a more prominent backup resource if El Niño reduces hydropower generation in the Pacific Northwest and solar generation in California this winter. Wind, geothermal, and nuclear power also present additional options to bolster the grid, though the effects of El Niño on wind generation remain poorly understood.

While a very strong El Niño could potentially alleviate some pressure on the electricity system by reducing winter heating demand in the northern U.S., Smith acknowledges that El Niño does not guarantee specific weather impacts. Severe cold outbreaks or major storms could still strain the grid, despite warmer-than-average winter temperatures. Smith emphasizes that while the overall averages are highly reliable, the day-to-day and week-to-week weather events that drive these averages remain less predictable.