Phoenix, Ariz. —  During the Arizona Corporation Commission’s Natural Gas Infrastructure and Storage Workshop, the state’s two largest electric utilities reported losing almost 1,600 MW of utility scale solar energy generation as the skies darkened during the height of Monday’s storms. 

Arizona Public Service (APS) and Salt River Project (SRP) officials say the loss of solar resources happened between 3:00 pm and 5:00 pm on Monday, August 25, 2025, during the peak demand hours.  APS reported a drop in solar energy generation amounting to about 1,000 MW, which is equivalent to about 50% of APS’ total utility scale solar fleet. At the same time, demand increased by 200 MW, further straining the system.  SRP officials reported they experienced a similar loss of about 45% of their utility solar resources at the peak of the storm, or nearly a 600 MW. 

"Imagine if 50% of our grid was required to be dependent on renewables as some have pushed," said Chair Kevin Thompson. "Arizona could be facing the reality of rolling brownouts on a severe weather event like we had Monday. Losing 1,600 MWs of generation that quickly is the equivalent to one of the units of the Palo Verde nuclear plant going offline. That's enough electricity to power roughly 350,000 homes during peak hours. Our workshop demonstrated why natural gas generation must continue to play a pivotal role in Arizona's energy mix, and how when properly combined with renewables we can keep the lights on."

During that time, APS and SRP both stated they relied on dispatchable natural gas resources that were able to come online quickly to compensate for the loss in solar output and maintain grid reliability. Without access to dispatchable natural gas resources, an estimated 350,000 homes could have lost power during the storm.  “Thanks to the flexibility and reliability of dispatchable natural gas generation, our utilities were able to keep the lights on and air conditioning running during Monday’s storm,” said Vice Chair Myers. “As we all know, solar output drops significantly during cloud cover or dust storms, making reliable backup generation essential.”

Monday's storm demonstrated the impact of unpredictable, severe weather events on the state's energy portfolio, and how the state's diverse mix of energy resources allowed the grid to remain reliable.