October 21, 2026
Key Points
- Direct current (DC) energy storage systems are evaluated with identified subsystems to applicable UL 9540 requirements.
- Compatible subsystem models are documented in the UL Product iQ® certification database.
- The pathway supports modular designs while simplifying certification and installation reviews.
When manufacturers use modular energy storage systems, they need a clear way to demonstrate that different components can work together safely. A new certification pathway from UL Solutions evaluates direct current (DC) energy storage systems with identified subsystems, including power conversion systems, and documents compatible configurations for verification by code authorities.
This approach is designed to reduce certification complexity while giving manufacturers greater flexibility in configuring energy storage systems.
What is a DC energy storage system?
A DC energy storage system captures energy for later use and can supply electricity to the grid or a building’s wiring system. These systems may be used for backup power for critical infrastructure or grid-scale energy storage.
Why are DC energy storage systems often modular?
A modular design allows manufacturers to combine different components based on the needs of a project. A DC energy storage system may be paired with subsystems such as power conversion systems. Confirming that the system and selected subsystems work together safely can add complexity to certification and installation reviews.
What is UL Solutions’ new certification pathway?
The new UL Solutions service evaluates a DC energy storage system with identified subsystems to the applicable requirements of UL 9540, the Standard for Energy Storage Systems and Equipment. The resulting certification documentation provides information about the evaluated configuration.
How is this different from a traditional certification approach?
The new pathway gives manufacturers an alternative to pursuing a full matched-assembly system listing at the outset. When a compatible subsystem is identified, the resulting certification documentation can provide manufacturers, developers and code authorities with information about the configuration evaluated by UL Solutions.
What does UL Solutions evaluate?
UL Solutions evaluates the DC energy storage system with each identified subsystem to applicable requirements of UL 9540. The evaluation addresses electrical safety, communication and interoperability between the system and each evaluated subsystem.
UL 9540 testing covers electrical, electrochemical, mechanical and other types of energy storage technologies used in systems that supply electrical energy. Its evaluation framework includes charging and discharging, protection, controls, communication between devices and other system-level considerations.
How are compatible configurations documented?
Compatible subsystem models are documented in the UL Product iQ® certification database under the DC energy storage system certification category. This documentation enables code authorities to verify combinations that UL Solutions has evaluated.
How can the pathway help manufacturers?
The new service can reduce certification complexity by documenting how the DC energy storage system and its identified subsystems were evaluated together. This documentation supports greater flexibility in modular DC energy storage system design.
How can the pathway support developers and code authorities?
Developers can use the resulting documentation to understand which system and subsystem combinations were evaluated. Code authorities can check the UL Product iQ database to verify compatible subsystem models documented under the certification category.
Can DC energy storage systems reduce energy conversions?
A battery energy storage system can reduce the number of times electricity must be converted between alternating current (AC) and direct current (DC). It can also simplify connections to solar panels, backup generators and other equipment.
Where can I learn more?
Additional information about the new service is available in the Oct. 20 press release.
More details are available in the certification pathway article and the Energy Storage System Testing and Certification service page at UL.com.