If you’ve been following the news on energy storage systems (ESS) or have recently looked into a home battery backup system, you’ve probably come across the term “UL 9540.” But what is UL 9540 and how important is it to ensure your home energy storage system is certified to this level?
What is UL 9540?
UL 9540 is a safety standard for energy storage systems. For energy storage systems connected to an electrical grid, the UL 9540 standard extends to the equipment used to make that connection. This standard addresses fire and explosion safety issues associated with ESSs, including:
- The safety of the storage component (battery) during operation
- Fire detection
- Spread and extinguishment of fires
- Effectiveness of Fire Mitigation in Confined Spaces
Since an ESS consists of several components, the UL 9540 standard actually encompasses two other older standards: UL 1973 (for the stationary battery) and UL 1741 (for the inverter). These two individual standards, together with rigorous thermal and electrical testing and evaluation of the components working together as a system, constitute the UL 9540 certification.
What is the difference between UL 9540 and UL 9540A?
While UL 9540 is a set of standards that an energy storage system must meet, UL 9540A is a thermal runaway evaluation method propagation in an ESS. So, although UL 9540A is not a certification, it provides important data for manufacturers seeking to have their ESS products certified to UL 9540 and for their engineers and product developers to verify the effectiveness of the protection. product against critical hazards such as fire.
There are four stages in the UL9540A test method:
- Cell test – Cells are tested for flammability, whether they can exhibit thermal runaway and the composition of gases released.
- Module testing – Groups or “modules” of cells are tested for the ability of thermal runaway to propagate from cell to cell, as well as outside the module.
- Unit tests – The potential for fire to spread from one unit to another is analyzed, as well as the rate of heat release and the composition of the gas to determine the explosion potential.
- Installation tests – The final stage tests unit to unit the spread of fire in a closed room with fire extinguishing equipment.
Is UL 9540 certification required for an ESS?
Certification of an energy storage system to UL 9540 is currently not required in most jurisdictions in the United States. However, the California building code has adopted the International Residential Code (IRC), which requires the UL 9540 standard for EHS. Massachusetts also recently adopted the code. We anticipate that it is likely that other cities and states across the country will follow these states and begin to require it in the years to come.
Even if UL 9540 is not required where you live, narrowing your energy storage system search to UL 9540 systems will bring benefits such as:
- Peace of mind knowing the system has been rigorously tested for safety
- Accelerate project authorization and approval with a single UL stamp across the entire system
- Revealing Which EHS Manufacturers Are Taking Safety Seriously and Planning for the Future by Obtaining UL 9540 Certification Now
Which ESSs are UL 9540 certified?
If you’re shopping for an ESS, don’t worry about UL 1973 and UL 1741 because as long as you see a “UL 9540” or “Certified to UL 9540” mark on an ESS guarantees that the system you plan to trust the home energy storage must be safe and designed to perform at a high level.
altE has made it easy to purchase a safe and high-performance ESS with our selection of UL 9540 certified energy storage systems from SimpliPhi, Sol-Ark, KiloVault, OutBack, Schneider and Enphase.