On Oct. 14, a rare solar eclipse will pass over much of the U.S., reducing midday sunlight. Grid operators like the Electric Reliability Council of Texas (ERCOT) and the California Independent System Operator (CAISO) have issued notices advising energy companies to prepare, as the cosmic event will significantly impact solar power generation. These unprecedented warnings highlight the deep interconnection between weather and renewable energy.
Below are screen captures of CAISO’s and ERCOT’s public notices from their websites.
ERCOT’s notice reveals how solar-heavy Texas could face major reliability and market challenges if the eclipse reduces photovoltaic output as expected. CAISO also warned the eclipse could create steep ramping needs and dual demand peaks across its footprint, especially with California’s growth in distributed solar.
As variable resources like wind and solar gain market share, disruptions that reduce their output require sophisticated preparation and coordination. Grid managers can no longer afford to be caught off guard by the rhythms of the skies. Events like eclipses underscore the importance of advanced forecasting, flexible portfolio management, and new operational thinking.
Why did grid operators issue these notices?
ERCOT now has over 5,000 megawatts of utility-scale solar capacity, while behind-the-meter rooftop solar has boomed in California. A solar eclipse can decrease PV output by 70-80% in impacted areas, creating a significant generation loss. Without proper preparation, this could strain grid reliability.
Dan Crawford, our senior director of Client Success, was the first to give PCI employees a heads up about the ERCOT notice in our #energy-industry Slack channel, where, every day, dozens of us discuss the latest energy news and industry trends.
“This [image above] shows Sunday, Oct. 8 (also a weekend day),” Dan wrote. “The fuel mix was over 30% solar mid-day (12-13 gigawatts), so this could be a very significant portion of the normal ERCOT generation during the impacted times.”
CAISO analysis predicts a steep 10,800 megawatts (MW) ramp in solar production over 90 minutes as the eclipse passes. The loss of rooftop solar could also create an unprecedented dual morning peak in demand. Careful coordination and planning are needed to manage these fluctuations.
For CAISO, it will be business as usual. I inquired about a comment from the ISO’s media department this week, and they happily obliged.
“The California ISO has been in constant communications with its stakeholders and market participants to carefully manage and mitigate the impacts of the solar eclipse,” said Anne F. Gonzales, CAISO’s senior public information officer. “We expect that our planning and coordination with stakeholders will protect the reliability of the grid during Saturday’s eclipse.”
ERCOT Communications provided a response as well:
“ERCOT does not expect any grid reliability concerns during the eclipse. On October 14, 2023, an annular solar eclipse will pass across the ERCOT region and impact solar Resource power production between 10:15 A.M and 1:45 P.M. CDT. Solar forecasts will continue to be updated as an hourly average to the date of eclipse: https://www.ercot.com/mp/data-products/data-product-details?id=NP4-737-CD.”
How should market participants respond?
To compensate for reduced solar output, participants may need to use more flexible conventional generation, stored power from batteries, shared reserves, demand response, and accurate eclipse impact forecasting.
What’s next for grid management?
Weather will increasingly impact supply and demand. Beyond solar eclipses, more natural disruptions may require special operational procedures, our president and COO, Javier Martin, told me.
“Heatwaves, hot weather alerts, wildfires, and extreme weather conditions are unfortunately becoming more common,” Javier said. “One that isn’t that common — and few people would associate with impacting the power systems are geomagnetic storms. I’ve seen few operational notices coming from the RTOs related to this and they always catch my attention. So we can say that RTOs have to be aware not only of Earth’s climatological conditions, but also space weather.”
However, early warnings like these notices from ERCOT and CAISO provide an essential line of defense, helping markets adapt smoothly.
This post covers the eclipse’s grid impacts, forecasting needs, and how participants can adapt. But with renewable growth accelerating, events like this highlight the need for sophisticated optimization tools to balance variable generation. Visit our Sustainable Energy page to learn how PCI’s renewable energy management solutions provide the forecasting, optimization, and trading capabilities needed to smoothly integrate variable resources like solar and wind.
