For many commercial and industrial battery projects in North America, the difficult part is no longer finding a battery with the required kWh.
The harder question is whether the proposed system can move smoothly through engineering review, fire-safety evaluation and local permitting.
That distinction matters.
A 261kWh cabinet and another 261kWh cabinet may look similar on a specification sheet. Both may use LiFePO4 cells, include liquid cooling and provide the same nominal energy. Yet the documentation available behind those two systems can be very different.
For an EPC or project developer, that difference may not become visible until the project reaches the Authority Having Jurisdiction (AHJ).
By then, changing equipment can be expensive.
This is why UL 9540, UL 9540A and NFPA 855 should increasingly be considered during BESS procurement—not after procurement.
UL 9540, UL 9540A and NFPA 855 Are Not the Same Thing
One of the most common mistakes in battery storage procurement is treating these three references as interchangeable.
They serve different purposes.
UL 9540 is the product safety standard covering the energy storage system and equipment. Its evaluation extends beyond the battery itself and considers areas such as charging and discharging, protection, controls, communications and interaction between system components. UL Solutions describes it as a comprehensive ESS standard that also references other relevant standards, including UL 1973 for stationary batteries.
UL 9540A, by comparison, is a test method.
Its purpose is to evaluate how an electrochemical energy storage system behaves when a cell enters thermal runaway and whether that event can propagate through the battery system.
Testing can examine behavior at different levels, including the cell, module, unit and installation level. The resulting information helps engineers and code officials understand heat release, gas generation, fire propagation and potential explosion hazards.
NFPA 855 deals with installation of stationary energy storage systems.
In practical project terms, it influences how an ESS may be installed and what fire and explosion risk controls may need to be demonstrated.
The three therefore form different parts of the same project conversation:
UL 9540 → system safety certification
UL 9540A → thermal runaway and fire propagation testing
NFPA 855 → installation requirements
For buyers, understanding that distinction prevents a dangerous assumption: that a battery-related certification automatically answers every question an AHJ may raise about the complete installation.
What Changed in 2026?
The safety framework continues to evolve as larger battery systems are installed closer to factories, commercial buildings, communities and other occupied areas.
A particularly important development is the sixth edition of ANSI/CAN/UL 9540A, published on March 13, 2026. UL Solutions states that the updated method expands guidance for installation-level large-scale fire testing.
The 2026 edition of NFPA 855 also places greater attention on areas including fire propagation prevention, explosion prevention and protection, system-level validation and technical documentation. UL Solutions notes that the updated framework involves interaction not only with NFPA 855 but also, where applicable, with NFPA 68 for deflagration venting and NFPA 69 for explosion prevention systems.
For project developers, this has an important commercial implication:
BESS safety is becoming increasingly installation-specific.
A supplier saying that its battery “passed a fire test” may not provide enough information to determine whether the proposed installation configuration is supported.
The project team needs to understand what was actually tested.
The Question Buyers Should Ask: What Exactly Was Tested?
Suppose an EPC is evaluating a liquid-cooled BESS for a commercial solar-plus-storage project.
The supplier provides a UL 9540A report.
That is useful—but it should not end the technical review.
The EPC should determine whether the tested configuration reasonably represents the equipment and layout proposed for the project.
Questions should include:
- Which battery cell was used in the tested system?
- What module and rack configuration was tested?
- Was testing performed at cell, module, unit or installation level?
- What enclosure configuration was evaluated?
- Were thermal runaway gases measured?
- Was propagation between cells or units observed?
- What separation conditions were used?
- What fire suppression or ventilation configuration was present?
- Does the commercial product being quoted match the tested configuration?
This is where procurement becomes engineering.
The goal is not simply to collect certificates. The goal is to establish a traceable relationship between the product being purchased, the system that was tested and the installation being proposed.
Why Large-Scale Fire Testing Matters
Battery fire behavior cannot always be understood from individual-cell performance alone.
When thermal runaway occurs, a cell can generate heat and flammable gases. At system scale, engineers also need to understand whether heat or fire can spread to neighboring modules, cabinets or other exposures.
Installation-level testing therefore looks at the behavior of a much more representative system.
UL Solutions explains that installation-level evaluation can examine the effectiveness of fire protection systems as well as heat and gas release and the risks of deflagration or re-ignition.
The 2026 edition of NFPA 855 includes updated Annex G guidance for implementing large-scale fire testing, while the sixth edition of UL 9540A expands the corresponding testing framework.
For large C&I and utility projects, these results can influence practical design decisions such as cabinet spacing, fire protection strategy, ventilation and the supporting documentation submitted to the AHJ.
Certification Should Be Reviewed Before the Purchase Order
In many battery projects, commercial evaluation happens first:
Price per kWh.
PCS power.
Battery capacity.
Cycle life.
Warranty.
Delivery time.
Certification documents are requested later.
For projects entering regulated North American markets, that sequence can create unnecessary risk.
A better procurement workflow starts by establishing the project compliance requirements before final equipment selection.
The project team should identify the jurisdiction, installation environment, system configuration and applicable codes. The manufacturer can then provide the certification and test documentation associated with the proposed product.
This allows the EPC and engineering team to identify gaps before the purchase order is issued.
It also changes how competing quotations are evaluated.
A lower equipment price does not necessarily mean a lower project cost if additional engineering, testing, redesign or permitting work is required later.
A Practical BESS Documentation Package
For a serious commercial project, buyers should expect more than a product brochure.
Depending on the project and jurisdiction, a technical package may include product datasheets, electrical single-line information, battery and PCS specifications, installation manuals, applicable certification records, UL 9540A reports, fire protection information, BMS architecture, communication protocols and system drawings.
Larger projects may require additional information addressing ventilation, gas detection, emergency shutdown, fire suppression or explosion risk.
The exact requirements should always be confirmed with the project engineer and local AHJ rather than assumed from a generic checklist.
That last point is important because North American permitting is not completely uniform.
The same BESS may encounter different review requirements depending on the state, municipality, project size, building environment and edition of the relevant codes adopted locally.
What This Means for BESS Manufacturers
The role of a battery storage manufacturer is also changing.
Supplying cells inside a metal cabinet is no longer enough for many commercial projects.
Developers increasingly need manufacturers that can support the engineering process around the equipment.
That means maintaining control over battery configuration, BMS logic, PCS integration, thermal management, fire protection and technical documentation.
It also means knowing which version of a product was tested.
At GSL ENERGY, this is particularly relevant when configuring commercial and industrial systems for different markets. A North American project may require a different compliance and documentation path from an otherwise similar project in Europe, the Middle East or Southeast Asia.
The electrical requirement may be similar.
The approval environment is not.
For this reason, certification should be treated as part of product architecture and project engineering, rather than simply as a marketing badge placed on a datasheet.
A Better Way to Compare BESS Suppliers
When comparing two battery energy storage suppliers, buyers should look beyond the headline specifications.
Start with five questions:
Is the complete system appropriate for the intended market?
Determine which certifications apply to the system being quoted—not simply certifications held by the company or by another product family.
Can the supplier provide the underlying test documentation?
A certificate tells only part of the story. For project engineering, the corresponding test configuration and reports may be important.
Does the tested configuration match the proposed equipment?
Changes in cells, modules, cabinet architecture or protection systems can matter.
Can the supplier support AHJ or engineering questions?
When a project reviewer asks for technical clarification, the manufacturer should be able to provide engineering-level answers.
Is compliance considered before system configuration?
This is particularly important when a project combines batteries, PCS, EMS, switchgear, transformers and fire-protection equipment from different sources.
These questions provide a much clearer picture of project risk than price per kWh alone.
The Bottom Line
The North American BESS market is moving toward more detailed evaluation of how battery systems behave at system and installation level.
The sixth edition of UL 9540A and the 2026 edition of NFPA 855 reinforce that direction.
For EPCs, developers and project owners, the practical lesson is straightforward:
Do not wait until permitting to investigate BESS safety documentation.
Review the certification path, tested configuration and supporting engineering documents while evaluating suppliers.
A battery energy storage system is not simply a collection of cells with a PCS.
For a commercial project, it is an engineered system that must work electrically, thermally, operationally—and within the approval framework of the market where it will be installed.
That makes compliance capability part of supplier capability.
Frequently Asked Questions
Is UL 9540A a certification?
No. UL 9540A is a test method used to evaluate thermal runaway and fire propagation behavior in battery energy storage systems. UL 9540, meanwhile, provides the product safety standard used for certification of complete energy storage systems.
What edition of UL 9540A is current in 2026?
The sixth edition of ANSI/CAN/UL 9540A was published on March 13, 2026. UL Solutions states that it expands installation-level and large-scale fire testing guidance.
Does NFPA 855 require UL 9540A testing?
UL Solutions states that UL 9540A is the fire and explosion test method specified in the 2026 edition of NFPA 855 and is referenced in its Annex G.11 guidance for large-scale fire testing.
Is UL 1973 the same as UL 9540?
No. UL 1973 addresses batteries used in stationary and other specified applications, whereas UL 9540 covers the broader energy storage system and equipment. A complete ESS evaluation therefore involves more than the battery pack alone.
What should an EPC request from a BESS supplier before ordering?
At minimum, the EPC should verify the product specification, applicable certifications, test reports, system configuration, installation requirements and the relationship between the tested equipment and the equipment being quoted. Project-specific requirements should then be confirmed with the engineer of record and local AHJ.
