What's New in NFPA 855 - 2026 Edition?

By Jocelyn Sarrantonio, PE | Technical Director at MeyerFire

These are exciting times in ESS Safety Land! The much-anticipated 2026 edition of NFPA 855: Standard for the Installation of Stationary Energy Storage Systems was made available last Thursday, ahead of schedule. You can read the new edition on NFPA Link now.

NFPA 855 RELEVANCE
If you don’t know what NFPA 855 is, it’s the ESS standard, first published in 2020, which is now on its third edition. The codes have been changing rapidly to keep up with the fire and explosion hazards of ESS, and although not outright adopted in most jurisdictions, NFPA 855 sets the standard for protection of ESS.

Because NFPA makes the drafts, proceedings of the Technical Committee, and the results of voting in the Conference Technical Session available to the public, we’ve had some previews about what the new code would include. The changes I was looking forward to learning about were those that would impact project designs and the level of involvement that fire protection engineers should have in project documentation, such as hazard mitigation analyses and emergency response plans.

​Having attended a lot of presentations on ESS in the past few years, the chatter was becoming quite loud that the current testing protocols were not going far enough, so it’s not surprising that new requirements were added there. I was also tuned into any changes in suppression requirements, having read through the motions that were to be voted on during this year’s Technical Session.

I’m sure the full industry impact will develop as time goes on, but now that it’s in writing, let’s take a first pass at some of the new provisions that will impact the ESS landscape. 

NEW BATTERY TECHNOLOGIES
First, NFPA 855 has been expanding the battery technologies that are specifically covered. This is important because there is a catchall entry for “All other battery technologies”, which can be conservative. So both the Threshold Quantities table in Chapter 1 and the Electrochemical ESS Technology-Specific Table in Chapter 9 have been updated with these new technologies.

FIRE AND EXPLOSION TESTING
First, the new 2026 edition of NFPA 855 has stricter fire and explosion testing protocols. Note that NFPA 855 refers to testing as “fire and explosion testing protocols” instead of just the “large-scale fire test” terminology that the IFC uses.

The requirements are relocated from Section 9.1.5 to Section 9.2, and titled “Fire and Explosion Testing.”
In 2023, the requirement stated:

“Where required elsewhere in this standard, fire and explosion testing in accordance with 9.1.5 shall be conducted on a representative ESS in accordance with UL 9540A or equivalent test standard.”

The 2026 requirement states:

“Where required elsewhere in this standard, fire testing in accordance with Section 9.2 shall be conducted on a representative ESS in accordance with UL 9540A and large-scale fire testing to collect data for gas production at a cell level, thermal runaway propagation potential at a module level, and thermal runaway propagation potential between ESSs.”

What has not changed is that not all ESS require fire and explosion testing, only when required elsewhere in the code, when we want to deviate from prescriptive requirements. Previously, these testing requirements really just pointed us to UL9540A, but now in 2026, the reference is to UL9540A and large-scale fire testing.

What’s that about?

UL9540A is the Test Method for Battery Energy Storage Systems (BESS), which is a protocol for testing ESS, initiates thermal runaway at the cell, module, unit, and installation levels of an ESS product, and collects the resulting data to help evaluate the fire and explosion hazards. However, as currently written, if a product passes at a given level, the test concludes and does not have to proceed to the next level. The argument against stopping the test is that the data collected may not present a realistic fire scenario, and therefore cannot truly be considered “large-scale”.

For example, if an external factor causes an incident, one that is not considered as part of the testing, then there is no data on how the ESS will perform in that scenario. Testing on ESS that does not proceed beyond the unit level does not provide any performance data in a larger failure scenario. The new wording in the 2026 edition requires the ESS to be tested per UL9540A and large-scale testing.

Annex G has been expanded, and Section G.11 is “Guidance on Implementing a Large-Scale Fire Test (LSFT)”. No other test standard besides UL9540A is noted here, but expect that document to be revised to catch up with revisions in NFPA 855.

Another addition to this section includes a requirement for ignition of vented gases in Section 9.2.1.2:

Where cell thermal runaway results in the release of flammable gases during a cell- or module-level test, an additional unit-level test shall be conducted involving intentional ignition of the vent gases to assess the fire propagation hazard.

Understanding what level of testing is expected by your jurisdiction will be a critical step in the ESS installation under NFPA 855-2026.

HAZARD MITIGATION ANALYSIS
Prior to 2026, there were several triggers requiring a Hazard Mitigation Analysis (HMA) in NFPA 855, most notably as a mechanism to exceed the maximum stored energy limits in Chapter 9. These HMA triggers were located in Chapter 4, which are general requirements meant to apply to all situations. Now, Section 4.4.1 has been re-written more broadly to require an HMA by default, unless otherwise modified in the subsequent technology-specific chapters.

What is the impact?

Previously, if you had a situation where you exceeded the Threshold Quantities for a given battery technology in Chapter 1, but were below the Maximum Stored Energy Limits, no HMA was required. Now that is not true, and essentially all installations require an HMA, except as modified by the technology-specific chapters. Because there is no longer a benefit of staying below the Maximum Stored Energy limits, the table is removed in the 2026 edition.

Although located in the Annex, the new edition also includes a recommendation that the HMA and fire risk assessment should be directed by a registered design professional. Put that PE license to work!

FIRE SUPPRESSION REQUIREMENTS
The changes made in Section 4.9 for Fire Control and Suppression are a little murkier. We are used to seeing a requirement for sprinklers as the default option, and alternate fire-extinguishing options may be permitted where they are supported by testing results. And to me, that’s how the 2023 edition read; sprinklers were the default option, and any other system type must have fire and explosion testing to support the design. There was a list of standards included for the following alternative system types: carbon dioxide (NFPA 12), water spray (NFPA 15), water mist (NFPA 750), hybrid water and inert gas (NFPA 770), clean agent (NFPA 2001), and aerosol (NFPA 2010).

Now in 2026, some of the words were changed and removed. The word “alternate” is struck, and NFPA 13 is included in the list of Fire Control and Suppression Systems, essentially putting all the system types on equal footing. And the requirement to permit “other systems”, where supported by large-scale fire and explosion testing, was moved after the list of acceptable NFPA standards.

To my reading, in 2023, the “other systems” were the alternative systems, but now, with the relocation of the requirement, the implication is that the use of those systems is not an alternative, and they are free to be used, without the use of large-scale fire and explosion testing to support their design. That was surprising to me, but I’d love to hear if that is consistent with the committee’s intent. I know it was the subject of a floor vote at June’s NFPA Technical Meeting, so I’d love to be enlightened if I am misinterpreting the changes.

EMERGENCY RESPONSE PLANNING AND TRAINING
NFPA 855 previous editions included Emergency Response Plan requirements in Section 4.3, but they’ve been revised in 2026 to require the plan to be developed with the AHJ and be submitted prior to training of required personnel.

The reason I am highlighting this change is that I know a lot of times items like these can become a last-minute hot potato without a clear directive for who is responsible. But if you’re reading this far, you probably know a lot about ESS, so maybe it should be you! Sometimes it just takes a competent individual to work with stakeholders to develop a plan that satisfies local fire department requirements. 

As we dig further into the new NFPA 855, I’m sure we will uncover more changes that impact the ESS landscape. Annex G, for example, has been really developed to include a lot of helpful material. If you’re interested in this content, we have an upcoming course on MeyerFire University that will cover code provisions for ESS. See you there!