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How safe are large battery facilities?

When operating normally, battery energy storage systems (BESS) pose no risks to the surrounding community. But fires—while rare and getting rarer—can be very harmful without the right precautions to prevent and contain them.

August 5, 2026

As the cost of batteries plummets, battery energy storage systems (BESS) are increasingly helping the world smooth out the bumps in our electricity supply. Last year, batteries added more new capacity to the world’s electric grids than any energy source other than solar power.¹ Because a BESS can start discharging energy in a fraction of a second, it can respond faster than any power plant to sudden swings in supply and demand, like a downed power line or an AI data center quickly ramping up its calculations. BESS are especially useful as solar becomes a larger part of our energy system, helping us capture more cheap, clean energy from the midday sun than we can immediately use.

There are now hundreds of these facilities in the U.S., located in almost every state,² and the stock is growing fast: Roughly a third of the country’s entire BESS capacity was added just in 2025.³ But as these BESS spring up in new areas, residents often wonder whether it’s safe to live near a large collection of powerful batteries.

“Fire is the biggest concern,” says Juner Zhu, an assistant professor of mechanical and industrial engineering at Northeastern University and co-founder of the MIT/Northeastern Center for Battery Sustainability.

Zhu studies how batteries can be designed and monitored to minimize fire risks. And although he spends much of his professional life thinking about battery accidents, he says he’d be comfortable with a BESS coming to his town. “As long as it’s an outdoor installation, and it’s far enough away from the community, I wouldn’t be alarmed,” he says. New facilities have multiple layers of protection, he adds, to stop fires from breaking out and contain them quickly if they do.

Still, just as you’d want to know the worst that could happen if an oil refinery or a natural gas pipeline were built in your town, it’s good to understand the worst-case scenario for a battery fire. For example, a major accident took place in Moss Landing, California, in January 2025, when residents were forced to evacuate as a fire consumed the country’s largest BESS.

Battery fires are hard to fight, says Zhu. The most serious fires result from a process called “thermal runaway,” when a battery cell grows hot enough to trigger chemical reactions that generate even more heat. This can cause gases to build up, the battery to burst, and a fire to leap from cell to cell. In this condition, even if a battery is extinguished, its electrolyte—a liquid that carries charge from one end to the other—can reignite itself.

“If you try to use water to extinguish it, it's not going to work,” Zhu says. Usually, firefighters wait the fire out, keeping people out of harm’s way and spraying nearby structures to prevent spread.

These long-burning fires create a secondary risk of toxic smoke and soot. A BESS is not like a coal plant or an oil refinery, which creates air pollution in the normal course of running: If nothing goes wrong, there’s no reason living near a BESS should affect your health. But there are toxic compounds inside batteries, and others can be produced in a fire, so areas exposed to smoke need to be evacuated. After the 2025 fire, residents of Moss Landing complained of sore throats and headaches,⁴ and researchers traced toxic metals in nearby wetlands to soot from the fire.⁵

How common are BESS fires? The Electric Power Research Institute (EPRI) tracks BESS safety failures (including fires and near-fires that lead batteries to fail), and finds that the rate of accidents has fallen every year, even as these facilities are built faster and faster.⁶ In the U.S., EPRI has documented about five incidents a year on average since 2019, most of which are controlled quickly.

Four of those incidents were at Moss Landing, which demonstrates how BESS safety is tightly tied to the design of specific facilities. The industry is growing very fast, says Zhu, and even compared to 2020 when Moss Landing was brought online, “we have much more knowledge, and we have better control.”

That starts with the batteries themselves. Early BESS, including at Moss Landing, often used nickel manganese cobalt (NMC) batteries, a type of lithium-ion battery widely used in phones, computers, and electric vehicles. “NMC is considered to have a high energy density,” says Zhu, packing a lot of energy storage into a small, lightweight package—perfect for cars and handheld devices. But that energy density comes with risks: NMC can reach thermal runaway at a lower temperature than other battery chemistries, and some components release oxygen as they burn, providing fuel for fires to spread.

These risks are low enough that we don’t worry about fires when we carry our phones around, but in a BESS with tens of thousands of battery cells, it’s much more important to minimize even small risks. “In some places, NMC is no longer allowed for BESS,” says Zhu. “For the energy storage sector, we prefer lithium iron phosphate (LFP).” This heavier but more stable chemistry has a much higher ignition temperature than NMC, produces little oxygen when it burns, and is also cheaper and lasts longer. In the U.S., around 90% of newly constructed BESS now use LFP chemistry.³

Where and how BESS are built matters, too.

“It must be outdoors,” says Zhu. Some early BESS like Moss Landing packed many batteries together in an indoor facility. This makes it hard to contain fires to a single battery module. It can also make emergency response more dangerous: During another high-profile fire in Surprise, Arizona, in 2019, flammable gases built up in an indoor BESS, causing an explosion that injured four firefighters.⁷

Today, battery modules are typically built in isolation from each other. These BESS look like parking lots full of shipping containers, with small buffer zones between modules and larger ones from any surrounding structures. Each module has its own monitoring system and a system to extinguish small fires before they grow.

That monitoring is crucial, says Zhu, because battery failures do not have to escalate into disasters. A battery that overheats or even ignites can still be isolated and extinguished.

For early detection, says Zhu, “you need sensors to monitor them. There are voltage sensors, temperature sensors. My group works on pressure sensors.” Any of these can spot unusual behavior and trigger an automatic response, like cutting the flow of electricity or activating fire suppression.

“If you have 100,000 batteries, then maybe one battery has a quality problem,” Zhu adds. “The real task is not to guarantee that every battery will be 100% safe. It's to diagnose thermal runaway ahead of time, and prevent it from propagating.”

The final layer of protection is emergency response. BESS developers typically work with local fire departments to create specialized plans to safely isolate fires. In the U.S., first responders have an excellent record at protecting the public; to date, the 2019 Surprise fire remains the only documented example of BESS fire injuries.⁸

As the industry matures, many of these protections are being standardized. The U.S. Environmental Protection Agency maintains a list of standards for building and operating BESS and for preparing emergency response plans.

Still, these facilities are mostly regulated at the local level, and codes vary from place to place. If a BESS is under consideration in your town, Zhu recommends asking about its design and systems, and making sure local officials have confirmed that they’re up to date. “Consider going to meetings and looking at their designs,” he says. “Look at their monitoring systems, and look at their distance between batteries, and learn about what batteries they are using. Confidence will start from understanding and more transparent sharing of information.”

“I think BESS companies should feel responsible to give enough information to whoever is interested,” he adds. “Enough space, enough controls, I wouldn't be super worried.”

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