Four years ago this week, California’s power grid was so stressed by a heat wave that rolling blackouts affected hundreds of thousands of residents over two days. The same situation nearly happened again two years ago, when state officials issued 11 “flex alerts” asking businesses and homeowners to voluntarily reduce their electricity use to avoid rolling blackouts.
But this year, when a record heat wave hit the state for three weeks from mid-June to July, sending temperatures above 110 degrees in the Bay Area and Central Valley, there was plenty of power. No warnings. No shortages. No flex warnings.
According to experts, this is largely due to the boom in the construction of giant battery projects.
California’s high-tech battery centers, built with thousands of lithium-ion batteries similar to those in cell phones and electric cars, solve the central problem in the push for more renewable energy: the fact that the sun doesn’t shine at night.
Battery storage capacity has increased sevenfold in the past five years in California, from 1,474 megawatts in 2020 to 10,383 megawatts today. One megawatt is enough electricity to power 750 homes.
In the past, when the sun went down each summer evening, the massive solar farms would stop producing electricity, sometimes leading to statewide blackouts in the early evening. Today, a growing number of battery storage plants across the state are storing that solar energy during the day, when it’s plentiful. The battery storage plants then release it back into the grid in the evening, when the sun goes down. But the heat is keeping demand for electricity high as millions of Californians rely on air conditioning.
“It’s like a bank account for energy,” said Elliott Mainzer, president and CEO of the California Independent System Operator, a Folsom-based agency that manages the state’s power grid. “In the middle of the day, you make big deposits. At the end of the day, we take money out of that account.”
Since 2020, California companies have built more large-scale battery storage projects than anywhere else in the world except China. Five years ago, the state had 36 such plants. Today, there are 175, with dozens more planned or under construction.
“It’s definitely been a game changer in terms of improving reliability,” Mainzer said.
This change took many people by surprise.
“These facilities are not very attractive. They’re not visible,” said David Hochschild, chairman of the California Energy Commission. “They’re out of sight. Their footprint is very small. They’re out of sight, but not out of mind.”
“They made the difference,” he added. “They’re the reason we didn’t have any bending alerts. Those storage facilities provided incredible protection.”
Most of the largest battery plants are in the Southern California desert, near Palm Springs, Blythe and Lancaster. But two of the largest are in Monterey County, at the site of the former PG&E Moss Landing Power Plant.
The natural gas plant, built in 1950 and famous for its two 500-foot-high concrete smokestacks, now houses a 750-megawatt battery storage plant owned by Vistra, a Texas company, and a 182-megawatt plant owned by PG&E. They are two of the largest such plants in the world. Vistra claims its plant is the largest in the world.
The PG&E plant houses 256 Tesla “Megapack” units. These shiny white steel boxes, each about the size of a shipping container and weighing 25 tons, were built at Tesla’s Gigafactory near Reno. Arranged in neat rows and set on concrete slabs, they are cooled by fans that hum in the background. The battery storage plant opened in 2022, and its storage provides enough electricity for 136,000 homes.
“This is a strategic location to connect to the grid,” PG&E spokesman Paul Doherty said during a tour Thursday. “All the cables and substations are here. And there’s room to expand.”
Tesla opened a new battery factory in Lathrop, south of Stockton, in 2022, which can produce about 13,000 Megapacks per year.
But this technology is not without controversy.
Fires broke out at the Vistra plant on September 4, 2021 and February 14, 2022. Investigations showed that they were caused by a malfunction of a sprinkler system, which released water and caused several units to overheat.
Then, in September 2022, a fire broke out at PG&E’s Elkhorn battery plant. Police closed Highway 1 for 12 hours. An investigation revealed that the fire was caused by an improperly installed ventilation screen on one of the 256 units, which allowed rainwater to enter and short-circuit the batteries. There were no injuries to firefighters, PG&E employees or the public.
Subsequently, Governor Gavin Newsom signed a law requiring battery storage plants in California to develop emergency response plans with local fire departments and strengthen fire safety.
“Increasing the state’s battery storage is critical to meeting our clean energy goals,” said Sen. John Laird, a Democrat from Santa Cruz who authored the bill. “But we also need to ensure that these facilities have safety systems in place to protect the health and well-being of workers and surrounding communities.”
Last month, after two fires at battery storage facilities in San Diego County, county officials demanded that officials develop stricter rules that would limit battery storage facilities near homes, schools and other facilities. And when Vistra proposed building a large battery plant in Morro Bay, area residents put a measure on a November ballot to determine whether it should be allowed.
Such fires are rare, said Mark Jacobson, a professor of environmental engineering at Stanford University. And by helping the state expand its renewable energy, they reduce the amount of electricity generated from natural gas, which in turn reduces soot and smog.
“In California, 12,000 people die every year from air pollution,” Jacobson said. “Nothing is perfect, but if we want energy, this is the best way to get it.”
In an effort to reduce greenhouse gas emissions and air pollution, California political leaders are increasingly requiring large utilities like PG&E, Southern California Edison and San Diego Gas & Electric to generate more and more electricity from renewables.
In 2018, former Gov. Jerry Brown signed a law requiring 100% of the state’s electricity to come from carbon-free sources like solar, wind, geothermal, hydroelectric and nuclear by 2045. Today, the state is at 61%. To make renewables more reliable, state regulators have required utilities to build or contract with companies to build battery storage. Today, utilities make money by buying electricity cheaply in the middle of the day when it’s plentiful and selling it at a higher price in the early evening.
On some days this year, batteries have become the largest source of electricity on California’s power grid. On Wednesday, a record 8,320 megawatts of battery power were on the grid as of 7:35 p.m. — the equivalent of 16 natural gas-fired power plants operating at full capacity, or four nuclear plants the size of Diablo Canyon operating at full capacity.
“It’s all happened very quickly,” said Jacobson, the Stanford professor. “Just a few years ago, no one was talking about batteries on the grid. California really demonstrated for the first time how beneficial they can be.”
