One of the biggest myths about renewable energy is that it isn’t reliable. Sure, the sun sets every night and winds calm down, putting solar panels and turbines to sleep. But when those renewables are humming, they’re providing the grid with electricity and charging banks of batteries, which then supply power at night.
A new study in the journal Renewable Energy that looked at California’s deployment of renewable power highlights just how reliable the future of energy might be. It found that last year, from late winter to early summer, renewables fulfilled 100 percent of the state’s electricity demand for up to 10 hours on 98 of 116 days, a record for California. Not only were there no blackouts during that time, thanks in part to backup battery power, but at their peak the renewables provided up to 162 percent of the grid’s needs — adding extra electricity California could export to neighboring states or use to fill batteries.
“This study really finds that we can keep the grid stable with more and more renewables,” said Mark Z. Jacobson, a civil and environmental engineer at Stanford University and lead author of the new paper. “Every major renewable — geothermal, hydro, wind, solar in particular, even offshore wind — is lower cost than fossil fuels” on average, globally.
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Yet Californians pay the second highest rates for electricity in the country. That’s not because of renewables, but in part because utilities’ electrical equipment has set off wildfires — like the Camp Fire started by Pacific Gas and Electric’s power lines, which devastated the town of Paradise and killed 85 people — and now they’re passing the costs that come from lawsuits and burying transmission lines to their customers. While investigators don’t know for sure what sparked all of the wildfires that have ravaged Los Angeles this month, they’ll be scrutinizing electrical equipment in the area. Power lines are especially prone to failing in high winds, like the 100-mile-per-hour gusts that turned these Southern California fires into monsters.
Even with the incessant challenge of wildfires, California utilities are rapidly shifting to clean energy, with about half of the state’s power generated by renewables like hydropower, wind, and solar. The study compared 116 days in 2024 to the same period in 2023 and discovered California’s output from solar was 31 percent higher and wind 8 percent. After increasing more than 30-fold between 2020 and 2023, the state’s battery capacity doubled between 2023 and 2024, and is now equivalent to the juice produced by more than four nuclear power plants. According to the study, all that new clean tech helped California’s power plants burn 40 percent less fossil fuel for electricty last year.
Those batteries help grid operators be more flexible in meeting demand for electricity, which tends to peak when people return home in the early evening and switch on appliances like air conditioners — just when the grid is losing solar power. “Now we’re seeing the batteries get charged up in the middle of the day, and then meet the portion of the demand in the evening, especially during those hot summer days,” said Mark Rothleder, chief operating officer of the California Independent System Operator, the nonprofit that runs the state’s grid.
Another pervasive myth about renewables is that they won’t be able to support a lot more electric vehicles, induction stoves, and heat pumps plugging into the grid. But here, too, California busts the myth: Between 2023 and 2024, demand on the state’s grid during the study period actually dropped by about 1 percent.
Why? In part because some customers installed their own solar panels, using that free solar energy instead of drawing power from the grid. In 2016, almost none of those customers had batteries to store that solar power to use at night. But battery adoption rose each of the following years, reaching 13 percent of buildings installing solar in 2023, then skyrocketing to 38 percent last year. (That is, of the 1,222 megawatts of solar capacity added last year, 464 megawatts included batteries.) That reduces demand on the grid because those customers can now use their solar power at night.
Batteries also help utilities get better returns on their investments in solar panels. A solar farm makes all its money selling electricity during the day. But if it has batteries attached to the farm, it can also provide energy in the evening, when electricity prices rise due to increased demand. “That evening battery contribution is very key to the economics working out well,” said Jan Kleissl, director of the Center for Energy Research at the University of California, San Diego, who wasn’t involved in the new paper.
So utilities are incentivized to invest in batteries, which also provide reliable backup power to avoid blackouts. But like any technology, batteries can fail. Last week, a battery storage plant caught fire on California’s central coast, the largest of its kind in the world, but it only knocked out 2 percent of the state’s energy storage capacity. A grid fully running on renewables will have a lot of redundancy built in, beyond multiple battery plants: Electric school buses and other EVs, for instance, are beginning to send power back to the grid when a utility needs it — a potentially vast network of backup energy.
But here’s where the economics get funky. The more renewables on the grid, the lower the electricity prices tend to be for customers, according to the new study. From October 1, 2023 to September 30, 2024, South Dakota, Montana, and Iowa provided 110 percent, 87 percent, and 79 percent, respectively, of their electricity demand with renewables, particularly wind and hydropower. Accordingly, the three have some of the lowest electricity prices in the country.
California, on the other hand, got 47 percent of its power from renewables over the same period, yet wildfires and other factors have translated into higher electricity prices. The California Public Utilities Commission, for instance, authorized its three largest utilities to collect $27 billion in wildfire prevention and insurance costs from ratepayers between 2019 and 2023.
Climate change is making California ever more prone to burn — a growing challenge for utilities. But the state’s banner year for solar and batteries just poked a whole lot of holes in the notion that renewables aren’t reliable.