These are report-snapshot values, not a complete count of every battery failure. Annual events divided by installed GWh are not an individual site's failure probability. The public CSV has 23 events for 2025, versus 24 in the report; the versions are not combined.
The denominator does most of the moving
For a community considering a large battery installation, a falling incident rate sounds reassuring. But the numerator matters too: did incidents become rare, or did the amount of installed storage grow much faster?
In EPRI's October 2026 report, the recorded annual count falls from 26 to 24, a decline of 7.7%. The published capacity figure rises from 343 to 634 gigawatt-hours, up 84.8%. Divide one by the other and the result falls from 7.58 to 3.79 incidents per 100 GWh, a 50.1% decline. The large change in that ratio is not a halving of the incident count.
A useful ratio is not a site-risk forecast
The report tracks major internal thermal incidents in stationary lithium-ion storage, including utility and commercial or industrial installations. It is not a census of every malfunction, electric-car battery or home battery. Reporting is incomplete, and each incident counts once regardless of its severity.
The denominator is stored-energy capacity, not electricity generated, power in gigawatts or operating years. Newly installed capacity can enter the annual stock without having operated for a full year. We also could not independently verify that the proprietary capacity series covers every installation type in the incident count.
The fair reading is narrower than “batteries are half as dangerous”: in this report, recorded incidents fell slightly while the installed capacity denominator rose sharply between these two years. A decision about one installation still depends on its design, operation and consequences of a failure.
Sources, Method & Data
Snapshot and calculation. Four aggregate values come from printed pages 6–7 of EPRI report 3002034920, dated October 2026. Its PDF was created on October 8; the exact first-publication day was not established. This chart is a new explanation of 2024–2025 data, not a new incident count for October 2026. Each ratio is annual recorded events / cumulative installed capacity in GWh × 100. Changes compare 2025 with 2024. Input capacities are already rounded; two decimal places on the ratio do not imply extra measurement precision.
Source versions do not fully reconcile. The public stationary-storage CSV retrieved on October 10 carried a September 29, 2026 Last-Modified header. It contains 26 events dated 2024 and 23 dated 2025, versus 26 and 24 in the newer report. Some regional and confidential-case totals also differ. A version difference is plausible, but no case-by-case revision history resolves it. We reproduce the report aggregates, not a reconstructed current global total; no cases have been invented or added to the CSV.
Coverage and denominator. EPRI includes major thermal events caused by internal battery-system failures and excludes external causes such as wildfires. Some cases are confidential. The report's source figure cites Benchmark Mineral Intelligence's BESS Forecast Q1 2026, China Energy Storage Alliance and Korea Electrical Safety Corporation. The underlying capacity records were not independently accessible. Matching of utility, commercial/industrial and UPS coverage between numerator and denominator remains unverified. This simple annual quotient is not exposure in GWh-years, an individual failure probability, a severity-adjusted measure or the report's separate age-based analysis.
| Year | Recorded incidents | Capacity (GWh) | Incidents per 100 GWh |
|---|---|---|---|
| 2024 | 26 | 343 | 7.58 |
| 2025 | 24 | 634 | 3.79 |
Graphic and rights. Own calculation and original graphic using four published aggregate facts; no EPRI figure or layout reproduced. EPRI's report is © 2026, all rights reserved, not an open-licensed dataset. The accessible CSV is linked for source-version checking, not substituted for the report.