Updated at 4:42 p.m. ET on November 9, 2026
Like all batteries, the giant lithium-ion ones in electric cars eventually fade. Once they can muster just 70 to 80 percent of their original charge, they’re not very useful as car batteries anymore: They simply can’t get a vehicle far. But even a fraction of the energy needed to move a car is still a lot of energy—enough to, say, power the average house.
Go on Discord, Reddit, or GitHub, and hobbyists are sharing tips to revamp car hardware for exactly this purpose. Andrew Austin, who goes by Battery Man on YouTube, recently filmed himself connecting an old Nissan battery to the solar array at his parents’ U.K. home. “I’m not necessarily saying that everybody should hijack their parents’ house and stick an EV battery on the side,” he told me. But in this case, it worked. His parents collected enough energy to meet their own needs, and then sold some back to the grid.
Experts on car-battery reuse also are not saying that everybody should hijack their parents’ house and stick an EV battery on the side. (In fact, most of the ones I talked with cautioned against it.) But for the better part of a decade in Europe, whole rafts of EV batteries have been repurposed—with more formal technical and engineering support—to store energy that can power homes, businesses, and factories. As the EV fleet in the United States ages, more buildings here could soon be hooked up to old car batteries too.
Wearing out an EV battery can take 15 to 20 years, which means that, by the mid-2030s, millions of EV batteries in the U.S. will be past their prime and ready for reuse. Connected to a building instead of a car, they can provide power during an outage, relieve strain on the electricity grid, and cut down utility bills by storing cheaper energy to pull from during hours of peak demand.
These kinds of projects can take many forms. In 2017, for instance, a green-energy company installed used batteries from the car manufacturer Renault in U.K. homes that already had solar panels, so they could store energy from the sunniest hours for later. In 2019, a German Audi factory equipped its forklifts with retired batteries from its own cars. A soccer arena in Amsterdam has a backup power system made of new and used Nissan batteries, as does the city of Melilla, Spain. One reason Europe capitalized on aging car batteries before America is simply that EVs achieved popularity there first. The European Union also has laws requiring automakers to trace, repossess, and dispose of old batteries, which encourages reuse.
In the U.S., the standard practice is to recycle EV batteries or send them to landfills, where toxins can leak into soil and water. But conditions are gradually becoming more favorable for reuse. Colorado and New Jersey both recently passed producer-responsibility laws resembling the EU’s. Over the past 10 years, the number of Americans with solar panels, who might therefore want a giant battery installed on their property, has soared. At the same time, new batteries have become more expensive to manufacture, partly because of President Trump’s steep tariffs on materials such as graphite. So reusing existing batteries makes economic sense. The AI industry is also investing in EV-battery reuse to meet the massive energy demands of data centers, which can burden the grid and saddle nearby residents with higher electricity bills.
At least a handful of start-ups are eager to sell Americans old batteries as a backup energy source, especially with weather-induced outages on the rise. “We literally have hundreds of gigawatts of battery supply driving on our roads today,” says Eddy Chiang, the CEO of Moment Energy, a company that prepares EV batteries for reuse and installs them for clients such as hospitals and airports. In 2024, for instance, the company installed a system using retired EV batteries to fast-charge cars at Vancouver International Airport.
Moment, like its fledgling competitors, is building on its close ties to the car industry: Its chief technology officer previously worked at Tesla, as did one of its strategic advisers. Last month, Redwood Materials, a company that recycles old EV batteries and builds reused-battery storage systems for data centers, declared that it was working to deploy used batteries from the electric-car maker Rivian at its own manufacturing facilities. Redwood also recently erected a microgrid in Nevada to power four data centers and plans to expand the operation to 20 more. A spokesperson told me the company anticipates that retired EV batteries will power half of the energy-storage market by 2030.
That estimate may be optimistic. A Stanford study from 2024 found that lithium-ion EV batteries might have a longer life than previously thought. Carmakers also purposely design batteries to be difficult to take out for liability reasons, Asaad Kaadan, an associate professor of electrical and computer engineering at the University of Tulsa, told me, so prying them out can be more of a hassle than it’s worth. After all, lithium-ion batteries aren’t risk-free. Last year, thousands of them (not sourced from EVs) burst into flames at a California energy-storage facility.
For now, companies installing giant batteries at people’s homes tend to rely on new ones. Vermont’s largest utility provider, Green Mountain Power, offers home-battery installation using Tesla Powerwalls and other similar systems, Mari McClure, the CEO, told me, although she would be open to working with companies such as Moment and Redwood in the future to outfit houses with old EV batteries. No one in the U.S. is yet marketing old EV batteries straight to homeowners. “It is one thing if a dedicated battery facility burns down, but it’s a whole other thing if someone’s home burns down,” Kenneth Gillingham, a Yale economist specializing in environmental and energy issues, told me. If you have an aging EV and a DIY spirit, though, no one can stop you from trying.
This article has been updated to clarify details about Green Mountain Power’s home-battery-installation program.