UL 9540 Energy Storage Systems Standard: An Overview

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UL 9540 covers energy storage systems and equipment. In this guide, we explain what importers and brands must know about this standard, including its scope, maximum energy capacity requirements, and lab testing.

Notice that this guide is written only based on publicly available information on this page. You need to buy the standard in order to access the contents of UL 9540.

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What is UL 9540?

UL Solutions, also known as Underwriters Laboratories, developed UL 9540 – Energy Storage Systems and Equipment. The standard covers energy storage systems (ESS) that supply electrical energy to local electric power systems (EPS).

In particular, the standard aims to assess how safe and compatible each integrated part of an energy storage system is.

The standard doesn’t cover individual components (e.g. batteries). Instead, it evaluates the safety and compatibility of these components when integrated into the system.

Both the American National Standards Institute (ANSI) and the Standards Council Canada (SCC) have approved UL 9540.

Which products are covered by UL 9540?

UL 9540 covers types of energy storage systems designed for the intake and storage of energy that will then be provided to loads or EPS as necessary.

The standard covers energy storage systems such as:

  • Electrochemical ESS
  • Chemical ESS
  • Mechanical ESS
  • Thermal ESS

UL 9540 covers systems for the following type of installations:

  • Stationary indoor installations
  • Stationary outdoor installations
  • Mobile ESS

This standard does not cover systems that use lead acid or nickel-cadmium (Ni-cad) batteries, which are covered by UL 1778.

Is UL 9540 mandatory in the United States?

UL standards are often voluntary. However, several electrical and residential codes require ESS to be listed according to UL 9540.

Thus, if you need to comply with the requirements of an electrical or residential code, you might need to ensure that your products comply with the requirements of UL 9540. This might be the case for importers and manufacturers of prefab homes in the US.

The standard lists eight different codes, including:

a. NFPA 70 – National Electrical Code (NEC)

b. ICC IRC – International Residential Code

c. IEEE C2 – National Electrical Safety Code


In this section, we provide some information concerning UL 9540, including maximum energy capacity and other requirements.


The standard covers outdoor, indoor and mobile installations, including:

a. Systems meant to be used in a standalone mode, including “self-supply” and “grid-supply” systems

b. Applications that carry out supplementary modes related to the production of power

UL 9540 notes that an ESS mainly consists of the following:

  • Energy storage mechanism
  • Power conversion equipment
  • Balance of plant equipment

It also states that ESS may include equipment for:

  • Charging and discharging
  • Converting power
  • Systems that detect and suppress fire
  • Moving and containing fuels

Maximum energy capacity

ESS should not exceed their maximum energy capacity. These numerical values may vary from system to system. Here we list the maximum energy capacity for different electrochemical ESS:

a. 20 kilowatt-hours (kWh) (72 megajoules (MJ)) for outdoor wall-mounted electrochemical ESS

b. 20 kWh (72 MJ) for residential-use electrochemical ESS

c. 50 kWh (180 MJ) for nonresidential-use electrochemical ESS

Other requirements

The standard includes ESS requirements used in:

  • Residential installations
  • Non-residential installations
  • Wall-mounted applications

Under UL 9540, the construction of an energy storage system should result in either a piece of equipment that is one complete unit, or an assemblage of matching components that can form a system when connected.

Where can I buy UL 9540?

You can purchase the standard from any of the websites listed below to access its contents.


  • Secure PDF and Hardcopy Combo: USD 631
  • Secure PDF (Read Only): USD 505
  • Premium Hardcopy: USD 631


  • Hard copy: USD 631


You can purchase a PDF version of UL 9540 on ANSI’s webstore through a Standard Subscription.


  • PDF download: 486.40 EUR (with VAT) or 454.58 (without VAT)
  • Hard copy: 607.70 EUR (with VAT)


  • Hard copy: USD 631

Lab Testing

If you are an importer or manufacturer, you should ensure that your products are safe to sell and be used. As such, you may benefit from having your products tested, as this may be the only way to find out how safe your product is.

In this section, we explain whether lab testing against UL 9540 is mandatory, and how much it may cost.

Is UL 9540 lab testing mandatory?

According to UL Solutions, installation codes such as the International Residential Code and the NFPA 855 require energy storage systems to be listed according to the requirements in UL 9540.

A product is said to be “UL Listed” when UL has received samples from the manufacturer, performed the necessary tests, and determined that the product meets the necessary safety requirements. Listed products should also include the relevant. UL Mark.

Thus, if your products need to comply with a code that requires UL listing in accordance with UL 9540, testing is necessary.

How much does UL 9540 lab testing cost?

The cost of testing your ESS against the requirements in UL 9540 may vary depending on location and the complexity of your product. Though we could not find any publicly-listed prices for UL 9540 lab testing, you can contact one of the companies below for a quote.

UL 9540 Lab Testing Companies

Below we list a few companies that offer testing services against UL 9540.

UL Solutions

UL Solutions provides certification services against the requirements of UL 9540 for companies looking to ensure that their energy storage systems are compliant with the standard’s requirements.


TÜV SÜD provides certification and energy storage testing services against the requirements in UL 9540 and related standards (e.g. UL 1973).

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