Todd Karin was prepared when California’s largest utility shut off power to millions of people to avoid the risk of wildfires last month. He’s got rooftop solar panels connected to a single Tesla Powerwall in his rural home near Fairfield, California. “We had backup power the whole time,” Karin says. “We ran the fridge and watched movies.”

Californians worried about an insecure energy future are increasingly looking to this kind of solution. Karin, a 31-year-old postdoctoral fellow at Lawrence Berkeley National Laboratory, spent just under $4,000 for his battery by taking advantage of tax credits. He's also saving money by discharging the battery on weekday evenings, when energy is more expensive. He expects to save around $1,500 over the 10 years the battery is under warranty.

The economics don’t yet work for every household, but the green-power combo of solar panels plus batteries is popping up on a much bigger scale in some unexpected places. Owners of a rice processing plant in Arkansas are building a system to generate 26 megawatts of solar power and store another 40 MW. The plant will cut its power bill by a third, and owners say they will pass the savings to local rice growers. New York’s JFK Airport is installing solar plus storage to reduce its power load by 10 percent, while Pittsburgh International Airport is building a 20-MW solar and natural gas microgrid to keep it independent from the local utility. Officials at both airports are worried about recent power shutdowns due to weather and overload-related blackouts.

And residents of the tiny northern Missouri town of Green City (pop. 608) are getting 2.5 MW of solar plus four hours of battery storage from the state’s public utility next year. The solar power won’t go directly to townspeople, but instead will back up the town’s substation, reducing the risk of a potential shutdown. It’s part of a $68 million project to improve the reliability of remote substations far from electric generating stations.

“It’s a pretty big deal for us,” says Chad Raley, who manages technology and renewables at Ameren, a Missouri utility that is building three rural solar-plus-storage projects to better manage the flow of electricity across the local grid. “It gives us so much flexibility with renewable generation. We can’t control the sun or clouds or wind, but we can have battery storage.”

The first solar-plus-storage installations started about a decade ago on a small scale in sunny states like California, Hawaii, and Arizona. Now they’re spreading across the country, driven by falling prices of both solar panels and lithium-ion batteries the size of a shipping container imported from both China and South Korea. These countries have ramped up production efficiencies and lowered labor costs, leaving many US manufacturers in the dust. In fact, the price of building a comparable solar-plus-storage generating facility is now cheaper than operating a coal-fired power plant, industry officials say. In certain circumstances, the cost is equal to some natural gas plants.

“This is not just a California, New York, Massachusetts thing,” says Kelly Speakes-Backman, CEO of the Energy Storage Association, an industry group in Washington. She says more than 30 states have renewable storage on the grid. Utilities have proposed and states have approved 7 gigawatts to be installed by 2030.

Speakes-Backman estimates the unit cost of electricity produced from a solar-plus-storage system will drop 10 to 15 percent each year through 2024. “If you have the option of putting out a polluting or non-polluting generating source at the same price, what are you going to pick?” says Speakes-Backman.