NFPA 855: The Complete Guide to Stationary Energy Storage System Fire Safety
NFPA 855, published by the National Fire Protection Association, is the U.S. standard for safe battery energy storage installation. If you’re developing, permitting, or financing a BESS project, compliance is not optional. In fact, your local fire marshal, your insurer, and your interconnecting utility will all check it first. This guide covers what the standard requires. It also covers what changed in the 2026 edition, and how the rules differ for C&I and utility-scale projects.
Quick Answer: What This Standard Covers
In short, this fire-safety standard sets the installation rules for battery storage in the United States. It covers spacing, ventilation, detection, suppression, and hazard analysis. That applies to everything from small residential batteries to utility-scale plants. Local fire codes enforce it. In addition, most insurers and interconnecting utilities require proof of compliance before they approve a project.
At a Glance
- What it is: a National Fire Protection Association standard for stationary battery energy storage systems, first published in 2020, now in its 2026 (third) edition.
- Who enforces it: local Authorities Having Jurisdiction (AHJs), typically through NFPA 1 (Fire Code) Chapter 52 or the International Fire Code Section 1207.
- Who it applies to: residential, commercial, industrial, and utility-scale BESS. Specifically, the scope is set by battery chemistry and stored energy, not by project type alone.
- What triggers it: aggregate stored energy above chemistry-specific thresholds. For example, that’s 20 kWh for lithium-ion.
- What’s new in 2026: a default requirement for Hazard Mitigation Analysis, large-scale fire testing, and stricter explosion control provisions.
What Does NFPA 855 Cover?
The standard addresses the full lifecycle of a battery energy storage system. That covers design, installation, commissioning, operation, maintenance, and decommissioning. In practice, most project teams also focus on five specific areas:
- Separation and spacing — distances between battery units, and between the ESS and exposures like buildings, property lines, and other hazards
- Fire detection and suppression — smoke and gas detection, plus sprinkler or other suppression systems sized to the installation
- Ventilation — exhaust systems that keep flammable gas concentrations below dangerous thresholds
- Explosion control — deflagration venting or prevention systems for enclosed spaces
- Hazard Mitigation Analysis (HMA) — a documented assessment of thermal runaway, fire propagation, and toxic gas risks for the specific installation
NFPA 855 Scope and Applicability
The first step is confirming the standard applies to your system at all. Applicability depends on battery chemistry and total stored energy, not project size alone. That said, below-threshold systems may fall outside full requirements. Your AHJ makes the final call.
| Battery Chemistry | Below Threshold | At or Above Threshold |
|---|---|---|
| Lithium-ion | < 20 kWh aggregate (may be exempt) | ≥ 20 kWh triggers full NFPA 855 requirements |
| Valve-regulated lead-acid (VRLA) | < 70 kWh aggregate (may be exempt) | ≥ 70 kWh triggers full NFPA 855 requirements |
| Other battery chemistries | Threshold set per chemistry table (2026 lists chemistries alphabetically) | Confirm with your AHJ before assuming exemption |
These thresholds matter. They decide how early compliance planning needs to start. For example, a small server-room battery backup might stay under 20 kWh and avoid full requirements. Conversely, almost any commercial, industrial, or utility-scale BESS will clear these thresholds immediately—meaning planning must start at the design stage.
What’s New in the 2026 Edition
This standard runs on a three-year revision cycle. The 2026 edition, however, brought some of the most significant changes since its 2020 debut. Four changes stand out for project developers:
- Hazard Mitigation Analysis is now the default. Earlier editions required an HMA only in specific circumstances. The 2026 edition makes it the default requirement for most installations, with limited exceptions for well-understood chemistries like lead-acid.
- Large-scale fire testing (LSFT) plays a bigger role. Previous editions leaned on UL 9540A cell, module, and unit-level testing. The 2026 edition adds large-scale fire testing. In this test, a full unit burns under real-world conditions with suppression disabled. This validates worst-case performance.
- Explosion control tightens. Installations must now include an explosion control and prevention system built to NFPA 69. Alternatively, teams can document a performance-based alternative.
- Chemistry coverage expands. The 2026 edition lists more battery chemistries. It also drops the old subdivision between battery technologies and capacitor-based systems, which simplifies how a given product finds its threshold.
Model fire codes run about a year behind the NFPA’s own cycle. Because of this, this edition will feed into the 2027 editions of NFPA 1 and the International Fire Code. In practice, jurisdictions that adopt fire codes quickly may already reference 2026 requirements today.
NFPA 855 for C&I vs Utility-Scale BESS
The core framework applies the same way across project types. Practical requirements, however, shift with scale.
- Larger installations trigger stricter spacing and suppression requirements. Our C&I vs utility-scale BESS comparison covers the full picture. Utility-scale plants pack far more energy into open sites, so spacing tables scale up accordingly. C&I systems, meanwhile, sit next to occupied buildings and face tighter fire-marshal review instead.
- C&I systems usually sit close to occupied structures. As a result, local fire marshal review and building setback rules carry extra weight alongside these requirements.
- Utility-scale systems sit on purpose-built sites. Because of this, compliance centers more on large-scale fire testing data, explosion control, and emergency response planning coordinated with the local fire department.
- Both project types need UL 9540A test data. Otherwise, they can’t satisfy the engineering basis for spacing and suppression design.
How NFPA 855 Relates to Other Standards
This standard doesn’t work alone. It references and depends on several other standards. Confusing them is a common, costly mistake.
- UL 9540 — the product-level safety certification for a complete energy storage system. Compliance also requires UL 9540-listed equipment.
- UL 9540A — the test method that measures thermal runaway fire propagation. Its results, then, set the engineering basis for spacing and suppression decisions.
- IEEE 1547 — governs grid interconnection behavior for distributed energy resources. It sits outside this standard’s fire-safety scope, but it often appears in the same project approval package.
- NEC Article 706 — the National Electrical Code section covering electrical installation requirements for energy storage systems above 1 kWh.
- For the complete standards landscape, see our guide to ESS codes and standards for utility-scale BESS.
NFPA 855 Compliance Checklist
Use this sequence to build compliance into a project. Otherwise, you risk discovering requirements late, during permitting:
- Confirm applicability — check your chemistry and stored energy against the current threshold table.
- Then, select UL 9540-listed equipment with UL 9540A test data covering your configuration.
- Complete a Hazard Mitigation Analysis. The 2026 edition makes this the default requirement.
- Also, design spacing, ventilation, detection, and suppression to the applicable chapter for your chemistry and installation type.
- Add explosion control per NFPA 69, or document a performance-based alternative.
- Finally, engage your AHJ early. Local adoption varies by state and jurisdiction. So, confirm which edition applies before finalizing your design.
Key Takeaways: NFPA 855
In short, this standard sets the fire-safety baseline for every battery energy storage system in the U.S., from a home battery to a utility-scale plant. The 2026 edition raises the bar with mandatory hazard analysis and large-scale fire testing. Compliance depends on chemistry, stored energy, and project scale. Therefore, the earlier you plan for it, the fewer surprises you’ll hit during permitting.
Frequently Asked Questions
Is NFPA 855 a Law or a Standard?
NFPA 855 is a consensus standard, not a law by itself. However, it carries legal weight once a jurisdiction adopts it, typically through NFPA 1 or the International Fire Code. Because adoption varies by state and city, always confirm which edition your local AHJ enforces.
Does It Apply to All Battery Chemistries?
Yes. The standard is technology-neutral and covers lithium-ion, lead-acid, flow batteries, nickel-based systems, and others. Each chemistry gets its own energy threshold. Consequently, the same project might qualify for an exemption under one chemistry and not another.
What’s the Difference Between UL 9540A and NFPA 855?
UL 9540A is a test method. It measures how far a fire propagates inside a battery system. NFPA 855, meanwhile, is the installation standard that uses those test results to set spacing, suppression, and separation requirements. Ultimately, you need UL 9540A data to satisfy it, not the other way around.
Does Compliance Differ for C&I vs Utility-Scale BESS?
The core framework stays the same, but practical requirements scale with the project. Utility-scale plants face larger spacing tables and heavier reliance on large-scale fire test data. C&I systems, meanwhile, face tighter scrutiny from local fire marshals, because they sit closer to occupied buildings.
When Does the 2026 Edition Take Effect?
NFPA publishes new editions on a regular three-year cycle, and 2026 follows that schedule. Model fire codes typically adopt a given edition about a year later. Because of this, check with your local AHJ to confirm which edition governs your permit application today.
Related Reading
- C&I vs Utility-Scale BESS: The Complete Comparison Guide
- ESS Codes and Standards for USA Utility-Scale BESS
- UL 9540A Test Method: Complete Guide for BESS Manufacturers
- Understanding BESS Specifications: The Complete Guide
- Battery Energy Storage System Safety
- BESS Certifications: Compliance Guide & Checklist