What's Happening?
The 6th Edition of UL 9540A, published on March 13, 2026, introduces significant changes to the battery energy storage systems (BESS) safety certification process. This update marks a shift towards system-level
fire safety by incorporating large-scale fire testing (LSFT) to ensure that thermal runaway events in one energy storage system do not propagate to adjacent systems. This change addresses critical safety concerns, particularly in preventing escalation beyond the initial failure. The revised UL 9540A aligns with NFPA 855-2026, which emphasizes performance-based fire safety outcomes. The update requires demonstration of non-propagation between BESS units, satisfying large-scale fire testing expectations. However, UL 9540A does not replace performance-based engineering analysis nor fully characterize all fire dynamics required for site-specific approvals.
Why It's Important?
The introduction of system-level fire testing in UL 9540A is crucial for the energy storage industry, which is rapidly scaling to meet increasing demand and renewable integration. High-profile incidents, such as fires at large-scale energy storage facilities, have highlighted the need for robust safety measures. The updated certification process aims to enhance public confidence in the safety of large battery systems, which are integral to modern power infrastructure. By preventing thermal runaway propagation, the new standards help mitigate risks associated with energy storage deployments near communities and critical infrastructure. This evolution in safety certification is expected to influence regulatory practices and industry standards, promoting safer energy storage solutions.
What's Next?
As jurisdictions begin to adopt the updated UL 9540A requirements, manufacturers will face new compliance challenges. Questions regarding the speed of adoption by authorities having jurisdiction (AHJs), treatment of existing test data, and expectations for additional testing beyond certification will arise. Navigating this transition will require a clear understanding of the intersection between UL 9540A, NFPA 855, and CSA/ANSI C800:25 standards. Organizations that proactively engage with both certification and performance-based testing will be better positioned to demonstrate compliance and accelerate deployment. The energy storage sector must continue to evolve its safety standards to match its growth, and the latest UL 9540A update is a step in that direction.
