A Comprehensive Guide to the U.S. Codes and Standards for Energy Storage Systems (ESS)

June 28, 2024


This white paper provides an informational guide to the United States Codes and Standards regarding Energy Storage Systems (ESS), including battery storage systems for uninterruptible power supplies and other battery backup systems. There are several ESS technologies in use today, and several that are still in various stages of development.

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This white paper provides an informational guide to the United States Codes and Standards regarding Energy Storage Systems (ESS), including battery storage systems for uninterruptible power supplies and other battery backup systems. There are several ESS technologies in use today, and several that are still in various stages of development.

While various technologies, such as flywheels, fuel cells, compressed gas, and others, are either in use or development, the primary focus of most of the jurisdictional Authority Having Jurisdiction (AHJ) is currently being placed on electrochemical storage systems.

These same Codes – and many of the Standards cited – cover all of the currently available ESS technologies, and in some cases, there are additional Codes and Standards cited to cover those specific technologies. For the sake of brevity, electrochemical technologies will be the primary focus of this paper due to being the ESS choice of the vast majority of users. Technologies such as pumped hydro, compressed gas, fuel cells, and various methods of gravity storage are not covered in this paper.

Why do we have Codes and Standards?

A code repository is necessary to increase awareness and improve safety in the energy storage industry. Electrochemical energy storage has a reputation for concerns regarding the ventilation of hazardous gases, poor reliability, short product life, substantial cooling requirements, and high levels of periodic maintenance.

Like the newer lithium battery technologies, the traditional lead-acid technology has developed a stigma. While generally a safe product, damage presents the risk of fire. When damaged, lead-acid, lithium, and some other battery technologies may also leach corrosive chemicals such as mercury, cadmium, and lead into landfills and may contaminate water supplies and ecosystems. These chemicals are dangerous to human health and are expensive to clean up. Users desire a safe, cost-effective alternative that requires less maintenance and is environmentally sustainable.

Definition of Codes and Standards

What differentiates Codes from Standards is the usage. Codes are an overarching statement of best (and safest) practices for an entire industry or technology.

As seen in the provided definitions, a Code is a set (or collection) of mandatory regulations that are established and enforced by a governmental authority. This is generally a collection of safety practices and other associated Standards enforced for the purposes of safety and reliability.

Standards, on the other hand, are technology or product specific, and provide a method to verify that the technology or product meets or exceeds the minimum acceptable level of safety.

What we refer to as “Codes” are actually model Codes, published by one of several nationally recognized organizations, with the purpose of presenting the “best practice” for subjects covered by the intended area of application. Each model code presents the latest consensus information on its related subject. These model Codes are then reviewed and adopted by the various jurisdictions, and when accepted become the legal Code for that jurisdiction. There are several separate model Codes, covering a variety of applications. For the purposes of this paper, only the applicable fire Codes and their related Standards will be considered.

In some cases, these Codes are adopted on a statewide basis. In others, they may be adopted on a county-by-county, or city-by-city basis. In county and local cases, the jurisdiction is allowed to amend the Code to make it more stringent, but in no case may the jurisdiction reduce the Code if it is adopted in full by a higher authority.

There are two primary organizations in the United States that publish these model Codes:

National Fire Protection Association (NFPA)

The first to be organized was the National Fire Protection Association (NFPA), which was organized in 1896 by several men associated with fire insurance companies. Currently, NFPA sponsors over 300 consensus Codes and Standards covering many safety related areas.

International Code Council (ICC)

The second is the International Code Council (ICC). ICC was organized by merging three separate regional code writing organizations. In 1972, the Building Officials Code Administrators International (BOCA), the Southern Building Code Council International (SBCCI), and the International Conference of Building Officials (ICBO) created the Council of American Building Officials (CABO) and published a single cooperative code for residential construction. This code was not well received but led to the formation of a more comprehensive set of building Codes. In 1994, these three organizations merged to form ICC, and created a single set of Codes that had no regional limitations. The first “I-Codes” were published in 2000.

Every jurisdiction in the US has adopted either the NFPA Codes or International Code Council’s I-Codes. Currently (2023), there are eight states that adopt the NFPA 1 Fire Code, and forty-two that adopt the International Fire Code. Interestingly, although there are much more advanced Codes available, there are still several jurisdictions that are using the 2015 revisions of the Codes, and at least one that is still using the 2009 revision.

As one gains understanding of the increasing number of new battery chemistries, and the associated risk factors, it is hard to justify maintaining an outdated Code base unless that Code is regularly amended to maintain the intended safety aspects of the more recent Codes.

Storage Technologies and Electrochemistries

There are several basic groups of ESS technologies in use today. They are usually broken into categories such as Mechanical, Gravity, Electrical and Electrochemical. While some of these may somewhat bridge gaps between technology groups, these are generally recognized as the major categories for Code purposes. It should be noted that technologies falling under the “Gravity” section have very little mention in the Fire Codes.

National Fire Protection Association (NFPA)

The first to be organized was the National Fire Protection Association (NFPA), which was organized in 1896 by several men associated with fire insurance companies. Currently, NFPA sponsors over 300 consensus Codes and Standards covering many safety related areas.


Electrochemical Double Layer Capacitors (EDLC) – The EDLC is considered a “supercapacitor” or an “ultracapacitor.” It is an electrostatic-based system with two electrodes producing electrostatic effects with activated carbons. These ultracapacitors can store or deliver energy at tremendous rates.
Supercapacitors – This is a general term for electrochemical double-layer capacitors.


Sources: Ricardo Consulting, AABC, National Academy of Sciences, and ZincFive estimates

Lead-Acid (LA)

The Lead-Acid battery utilizes the chemical reaction between lead and sulfuric acid. During discharge, lead and sulfuric acid react to form lead sulfate and hydrogen ions. During charging, the lead sulfate and hydrogen ions recombine into lead and sulfuric acid. This cycle of chemical reactions between lead and acid allows the battery to store and release electrical energy.

Nickel-Cadmium (NiCd)

The Nickel-Cadmium battery is based on the redox reaction between nickel hydroxide (NiOOH) and cadmium (Cd). Nickel hydroxide is the anode in the battery, and cadmium is the cathode. When the battery is charging, the reaction is reversed, nickel hydroxide is reduced to metallic nickel, and cadmium is oxidized to cadmium oxide (CdO).

Nickel-Metal Hydride (NiMH)

The Nickel-Metal Hydride battery is based on a chemical reaction between nickel and hydrogen. When the battery is discharged, the nickel is oxidized, and hydrogen is reduced, releasing electrons to provide electrical power. The reversed reaction occurs when the battery is being charged, which causes the hydrogen to oxidize and the nickel to reduce, allowing electrons to be absorbed from an external source.

Nickel-Zinc (NiZn)

The Nickel-Zinc battery is the process of chemical reactions between the anode (nickel) and the cathode (zinc) to produce electrical energy. Specifically, the nickel anode reacts with hydroxide ions during discharge, releasing electrons and forming nickel hydroxide. These electrons then travel to the zinc cathode, which reacts with zinc ions, releasing more electrons and forming zinc hydroxide. This process is reversed during charging.

Zinc-Manganese Dioxide (ZnMnO²)

The Zinc-Manganese Dioxide battery is also known as a zinc-carbon or alkaline battery, a secondary battery that can be recharged and reused multiple times. It is an improved version of the non-rechargeable zinc-carbon battery commonly used in household devices like remote controls, flashlights, and toys. The primary components of a rechargeable zinc-manganese dioxide battery are the anode, cathode, and electrolyte.

  • The battery’s anode is composed of zinc metal or a zinc alloy. During the recharging process, an electrical charge is applied to the battery, and the anode’s zinc ions combine with the electrolyte’s hydroxide ions, thus producing zinc hydroxide. The manganese oxide on the cathode is then changed back to manganese dioxide. During the battery operation (and discharge when the battery is in use), the zinc atoms at the anode undergo an oxidation reaction, releasing electrons and forming positively charged zinc ions

Sodium (High Temperature)

The electrochemistry of sodium batteries is based on the intercalation of sodium ions in graphite anodes and the reduction of sodium ions at a metal-oxide cathode. During charge, sodium ions are inserted into the graphite anode, and during discharge, the sodium ions are released and reduced at the metal-oxide cathode. The main advantage of using sodium instead of lithium is cost, as sodium is much more abundant and less expensive than lithium.

  • Sodium Sulfur (NaS) – Sodium sulfur batteries are based on the redox reaction between sodium (Na) and sulfur (S). The reaction occurs in a cell with an anode
    of sodium, a sulfur cathode, and a molten lithium and sodium chloride electrolyte. When the battery is charged, sodium ions move from the anode to the cathode and react with sulfur to produce sodium sulfide. During discharge, the reaction reverses, and the sodium sulfide is converted back into sodium and sulfur. The electrochemistry of sodium sulfur batteries makes them very efficient and can store large amounts of energy. They are also highly durable and have a long life span.
  • Sodium Metal Chloride (Na NiCl2) – Sodium metal chloride batteries involve the transfer of electrons between the anode and cathode, resulting in the oxidation of sodium at the anode and chlorine reduction at the cathode. The electrolyte is actually a solid beta-alumina that separates the liquid electrodes. This process is reversed during charging.


Flow batteries are electrochemical cells that use two different liquid electrolytes stored in separate tanks and pumped through the cell. The electrolytes are typically held in flow cells and separated by a membrane that allows ions to pass through. During operation, the two electrolytes react in the cell, generating electrical energy. This energy can power various loads, including motors, pumps, and lights. The process can be reversed, allowing a flow battery to act as a generator and store energy for later use.

  • Vanadium Redox (VRFB) – Vanadium redox flow batteries are electrochemical energy storage systems that use a vanadium-based electrolyte solution. The vanadium electrolyte is stored in two tanks and is circulated through a cell stack. The cell stack consists of a series of electrochemical cells where oxidation and
    reduction reactions take place. During charging, oxidation occurs in the cell stack, causing the vanadium in the electrolyte to be oxidized. During discharge, the vanadium is reduced. This cycle allows the battery to store and release electrical energy as needed.
  • Zinc-Air (ZnO2) – The zinc-air flow batteries use zinc metal as the anode and air-breathing cathodes. The zinc metal is oxidized at the anode, releasing electrons that travel through the external circuit to the cathode. Oxygen from the air is reduced at the cathode, forming hydroxide ions. The hydroxide ions react with zinc ions in the electrolyte to form zincate ions, which are then released into the electrolyte. The zincate ions are then re-oxidized at the anode, and the cycle is repeated. This process is powered by the flow of electrons from the anode to the cathode, generating electrical energy.
  • Zinc-Bromine (ZnBr) – Zinc-Bromine flow batteries are based on the redox reaction between zinc and bromide ions in an aqueous electrolyte stored in two tanks separated by a membrane. During charging, zinc is oxidized at the anode, and bromide is reduced at the cathode, forming a zinc bromide complex. During discharge, the reaction is reversed. The energy is stored in the zinc bromide complex, which can be recharged several times.


Lithium batteries are rechargeable batteries that utilize lithium metal or compounds’ electrochemical properties to store energy. They are the most common type of rechargeable battery used in consumer electronics such as cell phones, tablets, and laptops. Lithium batteries are also used in electric vehicles, medical devices, and military applications. The electrochemistry of lithium batteries is based on the redox reaction between lithium and an electrolyte solution. In a lithium battery, lithium ions are stored in the cathode material and are released into the electrolyte solution during charging. As the lithium ions travel through the electrolyte solution, they react with the anode material to form lithium metal, releasing electrons. During discharge, the lithium ions travel back to the cathode and take electrons from the anode, creating an electric current. (There are over 20 “lithium” chemistries. These are the most widely used in stationary applications.)

Lithium Iron Phosphate (LFP) – Lithium Iron Phosphate (LFP) batteries rely on a reversible redox reaction between the active materials, lithium iron phosphate (LiFePO4), and carbon. Upon charge, lithium ions (Li+) are inserted into the anode (negative electrode) while electrons are supplied to the cathode (positive electrode). When the battery is discharged, the lithium ions are extracted from the anode and travel through the electrolyte to the cathode. This is where the electrons are recombined to form the LiFePO4 compound. During this process, the battery releases energy in the form of electricity.

  • Lithium Nickel Manganese Cobalt Oxide (NMC) – Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2 or NMC) batteries are rechargeable lithium-ion batteries that have become increasingly popular recently. In these batteries, the positive electrode, or anode, is made of lithium cobalt oxide (LiCoO2). The negative electrode, or cathode, is made of a combination of nickel, manganese, and cobalt oxides (NMC). Lithium ions move from the anode to the cathode during charging, depositing onto the negative electrode. During discharging, the lithium ions move from the cathode to the anode in the opposite direction. This process of shuttling lithium ions back and forth between the anode and cathode provides power for the battery.
  • Lithium Nickel Cobalt Aluminum Oxide (NCA) – Lithium Nickel Cobalt Aluminum Oxide (NCA) is a rechargeable lithium-ion battery that utilizes a specific combination of materials in its cathode, including lithium, nickel, cobalt, and aluminum oxides to store and release electrical energy. During discharge, lithium ions move from the anode to the cathode through the electrolyte, creating an electric current. Nickel and cobalt are known for their high energy densities, while aluminum helps stabilize the cathode structure. The NCA cathode chemistry offers several advantages, including increased energy density, a long life cycle, high operating voltage, quick charging, and thermal stability. NCA batteries are commonly used in electric vehicles, power tools, and portable electronics.
  • Lithium Titanate (LTO) – Lithium Titanate anodes have been known since the 1980’s. The cathode can be lithium nickel manganese oxide (LMO) or nickel manganese cobalt oxide (NMC) compound, while the anode replaces the graphite with lithium titanate formed in a spinel arrangement. During charging, lithium ions move from the anode to the cathode. During discharge, lithium ions move from the cathode to the anode. This movement of ions creates an electric current, which is used to power a device. Lithium titanate has good fast charge characteristics and performs well at low temperatures but exhibits lower energy density than other technologies and is safer than most lithium batteries. LTO is expensive when compared to other lithium batteries.

How Codes Are Applied

Starting with the NFPA 1-2018 and IFC 2018, the Codes introduced some measure of regulation to ensure the safety of installed Energy Storage Systems (ESS). Although there was limited regulation regarding batteries and their installation, maintenance, and explosion/fire control in earlier revisions of the Codes, it was relatively rudimentary compared to later Codes.

As the adoption of newer battery technologies increased, both NFPA and ICC recognized that these technologies required more stringent regulation. The AHJs were unfamiliar with lithium, sodium, and other new technologies and had limited or no understanding of their potential problems. NFPA had several conflicting Codes and Standards cited in their fire code and recognized that creating a unified Energy Storage System (ESS) Standard was the best way to deal with that issue. This led to NFPA 855, the single ESS Standard NFPA now recognizes. The IFC 2021 revision deals with ESS slightly differently but has a chapter (Chapter 12) dedicated to Energy Systems and a section (Section 1207) dedicated to Electrical Energy Storage Systems. The IFC 2021 essentially copies the Maximum Allowable Quantities table (1206.9) from the IFC 2018, adds Nickel-Metal Hydride and Flow batteries to the table, and reprints almost the same data. There are additional stipulations in the requirements of the IFC 2021, but ICC did not go to the same lengths as NFPA in their 2021 edition. The 2024 edition of the IFC is anticipated to be more closely aligned with NFPA 855-2023.

Both the NFPA 1 National Fire Code and the ICC International Fire Code have adopted significant enhancements to the earlier code language in their 2021 revisions. Many jurisdictions still utilize the 2018 and earlier revisions of the Fire Codes. Still, many jurisdictions with high data center density are adopting the 2021 revisions and/or implementing NFPA 855-2020 as their ESS standard. While the 2021 revisions of the International Fire Code is the most recent available today (Q3, 2023), the new NFPA 1-2024 Fire Code has just been released in September of 2023, and NFPA 855 has already been updated with the NFPA 855-2023 Standard.

In the case of a jurisdiction adopting either of these Fire Codes and their related Standards, there are significant restrictions on some Energy Storage technologies. Any technology not explicitly listed in the relevant tables (Table 9.4.1 in NFPA 855-2023, and Table 1207.5 in IFC 2021), and even some of those listed but not specified as having an unlimited allowable quantity in a given fire area, will have to be approved on a case-by-case basis. Some jurisdictions will not allow a lithium battery to be installed under any circumstances. In contrast, some will allow them with severe restrictions on where they are installed, how much capacity is allowed, and what type of lithium battery is being proposed.

As mentioned earlier, the cited Standards significantly influence the Codes and their implementation. It is necessary to highlight some of these Standards (other than NFPA 855) due to their importance to both Codes. Three of particular importance are UL 1973, UL 9540, and UL 9540A.

List of Major U.S Codes and Standards

This section provides a comprehensive list of major U.S. Codes and Standards. See Appendix A for a concise cheat sheet for Codes and Appendix B for Standards.

Building Codes

International Building Code (IBC)

IBC 2018 – The International Building Code (IBC) 2018 is the most widely used in the United States. It is a model code developed by the International Code Council (ICC) that establishes minimum regulations for building design, construction, occupancy, and use to ensure public health, safety, and welfare. The IBC 2018 contains regulations for building materials, energy efficiency, fire safety, structural design, and more.

IBC 2021 – The 2021 version of the IBC is the sixth edition of the code, first published in 2000. The IBC establishes minimum regulations for the construction and maintenance of buildings and structures and addresses areas such as the design of structural elements, the installation of mechanical systems, fire protection and life safety systems, and energy conservation. The IBC is the basis for local and state building Codes throughout the United States.

Life Safety Code (NFPA)

A set of Standards developed by the National Fire Protection Association (NFPA) to protect people from fire dangers. The purpose of the NFPA Life Safety Code is to provide a uniform set of Standards for fire prevention and safety in all types of buildings, including schools, hospitals, hotels, and other public and private structures. Most states and localities have adopted the NFPA Life Safety Code throughout the United States.

NFPA 101 – The NFPA Life Safety Code addresses minimum building design, construction, operation, and maintenance requirements necessary to protect building occupants from danger caused by fire, smoke, and toxic fumes.

Fire Codes

NFPA 1 National Fire Code (varies by jurisdiction)

NFPA 1 offers a comprehensive, integrated approach to fire code regulation and hazard management, covering everything from fire alarms and sprinkler systems to building and process hazards and life safety issues.

NFPA 1 – 2015 – The Fire Code, 2015 (NFPA 1, 2015), produced by the National Fire Protection Association (NFPA), is the foundation for many state and
city Codes. The NFPA 1, 2015, and local jurisdiction amendments form the state Codes. Adopting jurisdictions include Connecticut, Delaware, Florida, Massachusetts, Detroit, New Hampshire, Rhode Island, Texas, and Vermont.

NFPA 1 – 2018 – The Fire Code, 2018 (NFPA 1, 2018) is produced by the National Fire Protection Association (NFPA). This document provides the foundation for many state and city Codes. The state Codes form the NFPA 1, 2018, and local jurisdiction amendments. Adopting jurisdictions include Florida, Hawaii, Kentucky, Maine, Maryland, New Hampshire, Rhode Island, Nashville and Davidson County, and West Virginia.

NFPA 1 – 2021 – The Fire Code 2021 (NFPA 1, 2021), produced by the National Fire Protection Association (NFPA), provides the foundation for many state and
city Codes. The NFPA 1, 2021, and local jurisdiction amendments form the state Codes. Adopting jurisdictions include Connecticut, Delaware, Massachusetts, and
West Virginia.

NFPA 70 National Electrical Code

NFPA 70, National Electrical Code (NEC) is the benchmark for safe electrical design, installation, and inspection to protect people and property from electrical hazards. The NEC has been adopted in all 50 states.

NFPA 70 – 2017 – The 2017 edition of the code includes safety requirements for electric vehicles, solar photovoltaic systems, and more.

NFPA 70 – 2020 – The 2020 edition of the electrical code includes requirements for various electrical systems-related topics, such as conductor protection, grounding and bonding, overcurrent protection, and more.

NFPA 70 – 2023 – The 2023 edition includes the latest electrical safety requirements.

International Fire Code (IFC)

This model code developed by the International Code Council (ICC) provides fire safety regulations for constructing, protecting, and occupying new and existing buildings, structures, and premises. The IFC covers many topics, including fire prevention, fire protection systems, flammable and combustible liquids, hazardous materials storage, means of egress, and emergency planning. The IFC also includes provisions for testing, inspection, and maintenance of fire protection systems and requirements for fire safety in high-rise buildings. IFC – 2015 IFC – 2018 IFC – 2021

NFPA 1 National Fire Code (varies by jurisdiction)

The National Fire Protection Association. It is a non-profit organization that develops, publishes, and disseminates over 300 consensus Codes and Standards to minimize the possibility and effects of fire and other risks.

(This is a sub-set. There are too many individual Standards to list all of them.)

NFPA 12 – The NFPA standard on carbon dioxide extinguishing systems. This document provides requirements and guidelines for designing, installing, maintaining, inspecting, and testing carbon dioxide extinguishing systems.

NFPA 13 – The NFPA standard for installing sprinkler systems. It outlines requirements for designing, installing, and maintaining automatic sprinkler systems for fire protection.

NFPA 15 – The NFPA standard for water spray fixed systems for fire protection. This standard guides the design, installation, operation, and maintenance of water spray systems used for fire protection.

NFPA 17 – the NFPA standard providing safety requirements for installing, maintaining, and using gaseous fire suppression systems. The standard applies to systems that use halocarbon agents, CO2, or inert gas gaseous fire suppression chemicals to extinguish fires.

NFPA 68 – The NFPAs standard on the design, installation, maintenance, testing, and use of explosion protection systems. It is intended to minimize the effects of
explosions caused by releasing flammable gases, vapors, and dust.

NFPA 69 – The NFPA standard for preventing fire and explosions in hazardous locations. It covers the design, installation, testing, and maintenance of systems and equipment used in hazardous locations.

NFPA 110 – The NFPA standard for emergency and standby power systems. The purpose of this standard is to provide requirements for the proper installation and maintenance of emergency and standby power systems to ensure their safe and reliable operation during an emergency.

NFPA 111 – The NFPA standard for stored electrical energy emergency and standby power systems. This standard covers the design, installation, maintenance, and testing requirements of emergency and standby power systems used in healthcare facilities, industrial facilities, and other commercial and institutional buildings.

NFPA 750 – The NFPA standard on installing, inspecting, and maintaining water-based fire protection systems. The standard includes information on the design, installation, and maintenance of fire sprinkler systems, fire pumps, fire hydrants, and other water-based fire protection equipment.

NFPA 855 – The NFPA standard for designing, installing, and maintaining fire protection systems. It establishes requirements for the identification, inspection, testing, and maintenance of fire protection systems and assessing the fire protection system’s performance.


ICC – International Code Council

ASHRAE/ICC Std. 240 – ASHRAE/ICC Standard 240 is a standard developed by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) and the International Code Council (ICC) that provides requirements for fire-resistance ratings of roof/ceiling assemblies and roof/ceiling decks. It offers valuable guidance for protection from the spread of fire from one building to another and from the spread of smoke and heat from one area to another within the same building.

UL – Underwriters’ Laboratories

UL 94 – This standard outlines the flammability test procedures for materials used to manufacture components and parts in devices and appliances. It is a commonly used standard for testing the flammability of materials and products used in the electronics industry.

UL 263 – This standard provides for the safety of Fire Tests of Building Construction and Materials. It requires that building materials and products be tested and certified to meet specific fire safety requirements. The tests determine the material’s flame spread and smoke development characteristics, and the results are used to classify the material as either Class A or Class B.

UL 1741 – This standard applies to all types of inverters and other power conversion equipment operating photovoltaic (PV) systems. UL1741 ensures that inverters and related systems comply with the National Electrical Code (NEC) safety requirements. It also provides that the equipment is designed, tested, and labeled correctly to reduce potential PV system operating risks.

UL 1778 – This voluntary standard applies to installing Uninterruptible Power Supplies (UPS) and other related power systems. It outlines requirements for installing and operating such systems, including testing and maintenance, to ensure safe operation.

UL 1973 – ANSI/CAN/UL 1973:2022 Standard for Safety – Batteries for Use in Stationary and Motive Auxiliary Power Applications


  • These requirements cover battery systems as defined by this standard for use as energy storage for stationary applications such as for PV, wind turbine storage or for UPS, etc. applications. These systems shall be installed in accordance with NFPA 70, C22.1, or other applicable installation Codes.
  • The basis for UL 1973 is battery system safety testing and analysis, which determines if the battery system has any operational safety issues that must be managed or controlled to ensure safe operation. All electronics and/or software used to ensure safe operation must be tested to demonstrate that they can reliably manage the battery system safety

There have been two CRDs issued for compliance with UL 1973. These include:

  • i1973_3_20220902, dated 9/2/2022, which adds nickel-zinc batteries to the technologies covered by UL 1973 and specifies the testing parameters for all monobloc batteries in Annex H.
  • i1973_3_20230323, dated 3/23/2023, provides testing exceptions for nickel-based batteries tested per Section 7.12.1.

These CRDs are specific to nickel-based batteries used in typical stationary applications such as UPS, PV, etc.

UL 1974 – This standard is for fire protection systems, including fire alarm systems, emergency voice/alarm communication systems, and high-rise evacuation systems. The standard ensures the safety of occupants in buildings where fire protection systems are installed.

UL 2075 – This standard certifies that products used in hazardous locations are safe to use. The standard covers the construction, installation, and operation of devices used in hazardous locations, such as those with flammable gases, vapors, and liquids.

UL 9540 – ANSI/CAN/UL 9540:2023 Standard for Safety – Energy Storage Systems and Equipment


  • These requirements cover an energy storage system (ESS) that is intended to receive and store energy in some form so that the ESS can provide electrical energy to loads or to the local/area electric power system (EPS) when needed. Electrochemical, chemical, mechanical, and thermal ESS are covered by this Standard. The ESS shall be constructed either as one unitary complete piece of equipment or as matched assemblies, that when connected, in accordance with the manufacturer’s installation instructions,form the ESS. An ESS consists of at least an energy storage function and energy storage protective function. If the ESS includes multiple parts that are housed in separate enclosures, it shall be considered as a multi-part ESS covered by this Standard. Individual parts (e.g. power conversion equipment, a battery, etc.) of an ESS are not considered an ESS on their own. This Standard evaluates the compatibility and safety of these various components and parts integrated into an ESS. The ESS can be an AC ESS or a DC ESS as defined in this Standard.


As can be seen in the italicized section of the Scope statement, Individual components of an ESS do not require a UL 9540 listing. These components may be tested as part of a UL 9540 system and then be recognized or listed as a UL 9540 component.

The UL 9540 listing is applied only to a complete system, including the charging, storage, and inverter in a single system (even if it is in multiple modules).

System components, such as batteries, safety control electronics, etc., have to be tested (as in the case of batteries undergoing the UL 9540A Test Method) or tested/listed under UL 1973 or other relevant Standards.

UL 9540A – ANSI/CAN/UL 9540A:2109 Standard for Safety – Test Method for Evaluating Thermal Runaway Fire Propagation in Battery Energy Storage Systems



The test methodology in this standard determines the capability of a battery technology to undergo thermal runaway and then evaluates the fire and explosion hazard characteristics of those battery energy storage systems that have demonstrated a capability to undergo thermal runaway.


The data generated will be used to determine the fire and explosion
protection required for an installation of a battery energy storage system intended for installation, operation and maintenance in accordance with ICC IFC, NFPA 1, NFPA 70, IEEE C2, CAN/CSA C22.2 No. 0, and other codes affecting energy storage systems, and the manufacturer’s installation instructions.


Fire protection requirements not related to battery energy storage system equipment are covered by appropriate installation codes.

NOTE: This is NOT a Pass/Fail test!

As stated in the Scope of the document, the data collected during the testing will be evaluated and used to determine the appropriate level of fire and explosion protection required by the specific product. The testing follows a progressive test-level methodology, where a single cell (or monobloc, i.e., the smallest unit manufactured) is tested, and if no propagation is noted, the testing ends. If propagation occurs, the product advances to the next testing level (module) and is retested. This testing continues through the unit and installation levels until the propagation is controlled; the fire and explosion requirements are determined at this point. This, then, is the data that the AHJ uses to determine the requirements for installation in the applicable jurisdiction.

There have been ten CRDs issued for UL 9540A. In the interest of space, those will not be listed here, but it is recommended that the reader should familiarize himself with them. As seen by the number of CRDs published, UL 9540A is an actively evolving Standard that has (and will continue to) changed as new chemistries come into the marketplace and as experience proves that more aspects of the testing need to be explored.

UL 60950-1 – This is an international safety standard for Information Technology Equipment (ITE). This standard is used to test and certify ITE for safety compliance and is administered by Underwriters Laboratories (UL). This standard covers safety requirements for ITE, ranging from power supplies and cables to servers and other computer components.

UL 62368-1 – This safety standard includes audio/video, information, and communication technology equipment. This standard was published in 2017 and outlines safety requirements for various equipment, from consumer electronics to professional audio/video equipment. This standard replaces UL60065 and UL60950-1.

Looking Ahead

New Codes and Upcoming Code Updates

Many Codes are due for updated releases next year, which are very important in the ESS world. Among these are the NFPA 1 National Fire Code and the ICC International Fire Code, International Building Code, International Mechanical Code, and several more from ICC, all expected to be released late in 2023. In addition, the NFPA 101 Life Safety Code will be released in late 2023.

Many of the NFPA and UL Standards are either due for a revision release or are in the development cycle for release soon.

As a reminder, checking for the latest amendments or additions to the existing Codes and Standards is extremely important. For example, NFPA will issue Technical Interim Amendments (TIA), which supersede the language in the published document. UL issues Certification Requirement Decisions (CRD) to update the language in their Standards and add or remove requirements for compliance with the Standard in question. In both cases, these changes will be resolved by the Technical Committee responsible for the specific document and incorporated in the document’s next release.


In Summary

It is difficult to overemphasize the importance of maintaining an awareness and understanding of the relevant Codes and Standards affecting modern ESS systems’ selection, use, installation, and maintenance. There are many choices from a broad spectrum of solutions available. Some of these may present challenges in being acceptable to the local AHJ having jurisdiction over Fire Code enforcement, or potentially, even with the AHJ having jurisdiction over the Building Code that applies to their jurisdiction.

Knowing and understanding these Codes and Standards’ impact on implementing a given ESS could have significant financial and scheduling issues for the end user. There is a value in maintaining a knowledge of the most recent revisions and additions to these documents, as this is a rapidly changing landscape, and what is considered acceptable in the Codes and Standards today may change to an unacceptable risk in a very short time.

International Code Council (ICC), https://www.iccsafe.org/
National Fire Protection Association (NFPA), https://www.nfpa.org/
American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), https://www.ashrae.org/
Underwriters Laboratories (U.L.), https://www.ul.com/-Underwriter
Battery University, https://batteryuniversity.com/
Energy Systems and Energy Storage, http://www.eseslab.com/index
DOE/EPRI 2013 Electricity Storage Handbook in Collaboration with NRECA, https://www.sandia.gov/app/uploads/sites/163/2021/09/SAND2013-5131.pdf
Environmental and Energy Study Institute, https://www.eesi.org/papers/view/issue-brief-energy-storage

Appendix A: Codes

Next Revision
NFPA1National Fire Code20212024
NFPA30Flammable and Combustible Liquids Code20212024
NFPA70National Electrical Code20232026
NFPA72National Fire Alarm and Signaling Code20222025
NFPA101Life Safety Code20212024
NFPA400Hazardous Materials Code20222025
Next Revision
ICCIBC 21International Building Code20212024
ICCIEBC 21International Existing Building Code20212024
ICCIFC 21International Fire Code20212024
ICCIFGC 21International Fuel Gas Code20212024
ICCIMC 21International Mechanical Code20212024
ICCIPC 21International Plumbing Code20212024
ICCIPMC 21International Property Maintenance Code20212024
ICCIRC 21International Residential Code20212024
ICCIWUIC 21International Wildland-Urban Interface Code20212024
Next Revision
IEEEC2National Electrical Safety Code20232028

Appendix B: Standards

Next Revision
NFPA12Standard for Carbon Dioxide Extinguishing Systems20222025
NFPA12AStandard for Halon 1301 Fire Extinguishing Systems20222025
NFPA13Standard for Installation of Sprinkler Systems20222025
NFPA15Standard for Water Spray Fixed Systems for Fire Protection20222025
NFPA17Standard for Dry Chemical Extinguishing Systems20242027
NFPA68Standard on Explosion Protection by Deflagration Venting20232026
NFPA69Standard on Explosion Prevention Systems20192024
NFPA76Standard for Fire Protection of Telecommunications Facilities20202024
NFPA110Standard for Emergency and Standby Power Systems20222025
NFPA111Standard on Stored Electrical Energy Emergency and Standby Power Systems20222025
NFPA750Standard on Water Mist Fire Protection Systems20232026
NFPA770Standard on Hybrid (Water and Inert Gas) Fire Extinguishing Systems20212024
NFPA855Standard for the Installation of Stationary Energy Storage Systems20232026
Next Revision
UL263Fire Test of Building Construction and Materials2021UL does not publish new editions on a schedule.
UL268Smoke Detectors for Fire Alarm Systems2016
UL1741Inverters, Converters, Controllers and Interconnection Systems Equipment for Use with Distributed Energy Resources2021
UL1778Uninterruptible Power Systems2023
UL1973Batteries for Use in Stationary, Vehicle Auxiliary Power and Light Electrical Rai (LER) Applications2022
UL1974Evaluation for Repurposing Batteries2018
UL9540Energy Storage Systems and Equipment2023
UL9540ATest Method for Evaluating Thermal Runaway Fire Propagation in Battery Energy Storage Systems2019
Next Revision
IEEE1491IEEE Guide for Selection and Use of Battery Monitoring Equipment in Stationary Applications2012IEEE documents are updated on a ten-year cycle unless there is an amendment or corrigenda published.
IEEE1635IEEE/ASHRAE Guide for the Ventilation and Thermal Management of Batteries for Stationary Applications2012
IEEE1657Recommended Practice for Personnel Qualifications for Installation and Maintenance of Stationary Batteries2018
IEEE1679IEEE Recommended Practice for the Characterization and Evaluation of Energy Storage Technologies in Stationary Applications2020