The Electric Power Research Institute analyzed its battery energy storage system failure database and found that the global failure rate for lithium-ion BESS, measured per GWh, dropped 98% from 2018 to 2025 and 50% from 2024 to 2025. Annual failure rates now range from 0.04% to 0.14%, comparable to the roughly 0.1% annual failure rate for oil-filled electrical transformers. EPRI also reported that 93% of BESS safety incidents worldwide resulted in no injuries or fatalities, and none have occurred in the U.S. since an April 2019 explosion at an Arizona Public Service facility injured four firefighters.
Older systems remain a concern. Facilities commissioned before 2021 account for only 3% of global storage capacity, but EPRI says they tend to fail at higher rates than newer systems built under stricter codes and design practices. Lakshmi Srinivasan, an EPRI senior technical leader, said systems deployed over the past five years appear significantly more reliable, and that lessons learned since 2019 and 2020 have improved newer projects. The report also notes that indoor BESS facilities fail at higher rates and sustain more damage on average than outdoor ones, citing the January 2025 Moss Landing fire that destroyed most of a 300-MW array.
For owners of older facilities, EPRI recommends thorough risk assessments and possible retrofits. Explosion-mitigation measures can range from installing flammable gas detectors to larger ventilation or structural changes, though those may void manufacturer warranties. In some cases, early decommissioning may be the better option. Safety standards are also evolving: the National Fire Protection Association plans to replace NFPA 855 with NFPA 800, and New York now lets local authorities require developers to pay for independent technical reviews of exemption applications.