Monday’s solar eclipse will affect California’s power system for a couple of hours, but the state’s grid operator says utility customers in San Diego and across the Golden State will be largely unaffected and no energy conservation measures have been issued.
The California Independent System Operator, which manages the power system for about 80 percent of the state and a small portion of Nevada, does not anticipate any service interruptions on Monday — even though the amount of solar energy on California’s grid has increased sharply in recent years.
“We will ramp up generation to compensate for lost solar production, and there is plenty of capacity to meet need,” the system operator, also known as the California ISO, said in a post on its website of frequently asked questions about the eclipse.
On Monday, the moon will cross between the sun and the Earth, blocking the face of the sun. The eclipse will cast a 115-mile-wide shadow across 14 states from Texas to Maine in what’s called its “path of totality” in which observers will see the sun almost completely obscured for a few minutes — provided the sky is clear in those particular areas.
Western states, including California, will experience just a partial eclipse. San Diego may see 53.9 percent of the eclipse as it move north, according to NationalEclipse.com.
Since solar makes up about 20 percent of California’s in-state electricity generation during normal daylight hours, Cal ISO managers on Monday will see some big fluctuations on the system.
The eclipse will start to affect grid-scale solar generation and demand, or load, at 10:05 a.m. It will reach maximum impact between 11 a.m. and 11:20 a.m., before returning to normal operations at 12:40 p.m.
During a presentation last month about the effect of the eclipse, California ISO officials forecast that solar production will slump to 7,123 megawatts of production at 11:20 a.m. That’s more than 6,900 megawatts less than normal on a clear day.
But as the eclipse es, solar production will quickly ramp back up at a pace of 84 megawatts per minute and by 12:40 p.m., go back to supplying 13,840 megawatts of electricity to the grid.
“The predictability of the event will make it easier for ISO grid operators to manage the more intense ramps,” the grid operator said, adding that it has coordinated with utilities, natural gas companies and generators to manage the “rapid loss and return of solar generation during the eclipse.”
That includes procuring hydro-electric power, natural gas plants and battery storage resources that can ramp up quickly.
In a similar way, Monday’s eclipse will also affect production from customers who have installed rooftop solar on their homes and businesses. But a local installer said the overall impact will be negligible.
“If somebody’s watching their meter on a moment-to-moment basis, they’ll certainly see the production go down … and then go back up,” said Michael Powers, co-founder of Stellar Solar, based in Oceanside. “But because the eclipse will last for such a short period of time, in the big picture, production will be more or less not noticeable for (a customer’s) output of the entire month.”
The California ISO said it’s also taking lessons from earlier eclipses.
Last year on the morning of Oct. 14, an annular eclipse occurred — what’s commonly called a “ring of fire” eclipse, when the moon obscures all but an outer edge of the sun. Monday’s eclipse is classified as a total eclipse, in which the moon completely covers the sun. The last total eclipse that ed through the United States came in 2017.
During the 2023 annular eclipse, California’s grid experienced a similar drop in solar production and subsequent ramp-up without incident.
In the six months since the 2023 annular eclipse, California ISO reports the amount of utility-scale solar on its system has increased by 2,030 megawatts and the total of rooftop solar (known as behind-the-meter solar) has grown by 1,420 megawatts.
