An EPRI analysis found that energy storage system failures fell 98% between 2018 and 2025, though older systems still need special care.
The global failure rate for lithium-ion battery energy storage systems, measured per GWh, fell 98% from 2018 to 2025 and 50% from 2024 to 2025, the Electric Power Research Institute (EPRI) said in a new analysis of its BESS failure incident database. Stationary energy storage systems' annual failure rates range from 0.04% to 0.14%, according to the analysis, which is comparable to the 0.1% annual failure rate for oil-filled electrical transformers, EPRI said in the report, *Risk Factors and Failure Statistics of Lithium-Ion BESS*. Safety reviews and, in some cases, retrofits can mitigate failure risk and improve reliability in older systems, which tend to fail at higher rates than newer systems built under stricter codes and design practices, EPRI said.
Ninety-three percent of the BESS safety incidents EPRI reviewed worldwide resulted in no injuries or fatalities, according to the report. In the United States, no injuries or fatalities have been reported as a result of BESS failures since April 2019, when an explosion at an Arizona Public Service facility seriously injured four firefighters. A post-incident report by Underwriters Laboratories (UL), the global safety science organization, noted that the APS installation was commissioned before the initial release of NFPA 855, the safety standard that governs energy storage systems today. As soon as this fall, the National Fire Protection Association plans to replace NFPA 855 with NFPA 800, which it calls a "holistic" standard that incorporates lessons learned since the early days of BESS deployment.
Lakshmi Srinivasan, a senior technical leader with EPRI's energy storage program and a principal investigator on the report, told Utility Dive that battery systems deployed over the past five years appear significantly more reliable than earlier vintages, and that the trend continues today. "There are things we know in 2026 that were not necessarily understood in 2019 or 2020, when the older systems were being put in place," Srinivasan said in an interview.
The most dramatic BESS failure in the U.S. involved a utility-scale installation inside a 1950s-era turbine hall at a decommissioned thermal power plant near Santa Cruz, California, known as Moss Landing. In January 2025, thermal runaway in one of the units caused a fire to spread throughout the indoor facility and ultimately destroy most of the 300-MW battery array. Thick smoke emanated from the facility for days, but no injuries were reported, and subsequent soil and water monitoring found no significant threats to human health or the environment. Experts later told Utility Dive that the incident was a "learning opportunity" for the energy storage industry. Vistra commissioned Moss Landing in 2020.
Indoor BESS facilities fail at higher rates and sustain more damage on average than outdoor facilities, according to EPRI's report. Propagation-prevention measures within battery units, along with fire walls or similar barriers between units, can mitigate the spread of fire within indoor facilities, EPRI said. BESS facilities commissioned before 2021 account for just 3% of global energy storage capacity, according to the report. Srinivasan said it is worthwhile for owners of those older facilities to run thorough risk assessments and take corrective action if warranted.
The 2019 Arizona incident showed that older BESS facilities need to address explosion risk, which Srinivasan described as "a different risk than fire and a bigger one from a personnel and equipment standpoint." Explosion-mitigation retrofits range from what she called "a relatively low-difficulty change," such as installing flammable gas detectors inside battery enclosures, to more significant projects such as installing new ventilation systems or making structural upgrades that direct pressure waves upward and away from first responders. Those last two types of projects generally require changes to battery unit envelopes, which could void the manufacturer's warranty or interfere with other aspects of the system's design. In some scenarios, Srinivasan said, it could make more sense to prematurely decommission an outdated, higher-risk system.
Although newer battery systems appear safer than early-vintage systems, local permitting remains challenging in some jurisdictions. Limitations in the NFPA 855 standard lead most developers to apply for exemptions that allow higher energy densities or other project modifications, Srinivasan said. To help local authorities that may lack in-house expertise, New York added a requirement to its fire code, which took effect in January, allowing those authorities to make energy storage developers pay for independent technical reviews of exemption applications, she added.