Four years ago this week, a heat wave overwhelmed California’s power grid, causing hundreds of thousands of residents to experience blackouts in two days. It almost happened again two years ago, when state officials issued 11 “Flex Alerts” urging businesses and homeowners to voluntarily reduce their electricity use to avoid blackouts.
But this year, when a record heat wave hit the state for three weeks from mid-June through July — sending temperatures in the Bay Area and Central Valley into the 40s — there was plenty of power. No warnings. No shortages. No flex alerts.
According to experts, a key reason for this is the boom in the construction of huge battery projects.
California’s high-tech battery centers are equipped with thousands of lithium-ion batteries similar to those found in cell phones and electric cars. They solve the main problem facing renewable energy development: the fact that the sun doesn’t shine at night.
In California, battery storage capacity has increased sevenfold in the last five years, from 1,474 megawatts in 2020 to 10,383 megawatts now. One megawatt is enough to power 750 homes.
In the past, massive solar farms would stop producing electricity at sunset each summer evening, sometimes causing blackouts across the state in the early evening. Today, the proliferation of battery storage power stations across the state can store solar power during the day when it is in abundance. The battery storage power stations then release it back to the grid in the evening when the sun goes down but hot weather keeps electricity demand high as millions of Californians run their air conditioners.
“Think of it like an energy bank account,” said Elliott Mainzer, president and CEO of California Independent System Operator, a Folsom-based agency that manages the state’s power grid. “In the middle of the day, you deposit large amounts. At the end of the day, we deduct from that account.”
Since 2020, companies in California have built more large-scale battery storage projects than anywhere else in the world except China. Five years ago, there were 36 such facilities in the state. Today, there are 175, with dozens more planned or under construction.
“It has definitely fundamentally improved reliability,” said Mainzer.
This change has surprised many people.
“These plants are not sexy. They are not visible,” said David Hochschild, chairman of the California Energy Commission. “They are out of sight. The footprint is very small. They are out of sight, but not out of mind.”
“They made the difference,” he added. “They’re the reason we didn’t have any flex alerts. These storage facilities gave us an incredible cushion.”
Many of the largest battery factories are located in the Southern California desert, near Palm Springs, Blythe and Lancaster. But two of the largest are in Monterey County, on the site of the old PG&E Moss Landing power plant.
Built in 1950, this natural gas-fired power plant, known for its two 500-foot-tall concrete smokestacks, now houses a 750-megawatt battery storage plant owned by Texas-based Vistra and a 182-megawatt plant owned by utility PG&E. They are two of the largest such plants in the world. Vistra says its plant is the largest in the world.
The PG&E plant has 256 Tesla Megapack units. The shiny white steel boxes, each about the size of a shipping container and weighing 56,000 pounds, were built at Tesla’s Gigafactory near Reno. Arranged in neat rows and sitting on concrete slabs, they are cooled by fans humming 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 for grid connection,” PG&E spokesman Paul Doherty said during a visit on Thursday. “All the lines and substations are here. And there is room for expansion.”
Tesla opened a new battery factory in Lathrop, south of Stockton, in 2022 that can produce about 13,000 megapacks per year.
However, the technology is not without controversy.
Fires broke out at the Vistra plant on September 4, 2021 and February 14, 2022. Investigations revealed that the fires were caused by a malfunction of a sprinkler system that released water and caused several systems 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 found the fire was caused by an improperly installed vent guard on one of the 256 units, allowing rainwater to enter and short-circuit the batteries. There were no injuries to firefighters, PG&E employees, or the public.
Governor Gavin Newsom subsequently signed a law requiring battery storage facilities in California to work with local fire departments to develop emergency plans and increase fire protection.
“Increasing the state’s battery storage capacity is essential to meeting our clean energy goals,” said Senator John Laird (D-Santa Cruz), who authored the bill. “But we also need to ensure these facilities have safety systems in place to protect the health and well-being of workers and surrounding communities.”
Last month, after two fires broke out at San Diego County battery storage facilities, the San Diego County Executive asked county officials to draft 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, residents there brought a vote in November on whether to approve it.
Such fires are rare, says Mark Jacobson, a professor of environmental engineering at Stanford University. And by supporting the expansion of renewable energy in the state, they are reducing 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.”
In an effort to reduce greenhouse gas emissions and air pollution, California politicians have increasingly required major utilities such as PG&E, Southern California Edison and San Diego Gas & Electric to generate a larger share of their electricity from renewable energy.
In 2018, former Gov. Jerry Brown signed a law requiring that 100% of the state’s electricity come from carbon-free sources such as solar, wind, geothermal, hydroelectric and nuclear by 2045. Today, that figure is 61%. To make renewable energy more reliable, state regulators have required utilities to build battery storage or contract with companies to do so. Now, utilities make money by buying power at low prices during the midday hours, when it’s plentiful, and selling it at a higher price in the early evening.
On some days this year, battery power has been the largest source of electricity on California’s power grid. On Wednesday, as of 7:35 p.m., a record 8,320 megawatts of battery power were on the grid, the equivalent of 16 natural gas-fired power plants at full capacity or four nuclear power plants the size of Diablo Canyon at full capacity.
“It’s happened so quickly,” said Jacobson, the Stanford professor. “Just a few years ago, nobody was talking about batteries on the grid. California has really shown for the first time how useful they can be.”
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