By AGILE Consulting Engineers, Solar PV and Battery Energy Storage Systems (BESS) specialists.
A battery energy storage system (BESS) doesn’t fail like a transformer or an inverter. When a lithium-ion cell goes into thermal runaway, the fault can propagate through an entire rack before anyone on site has time to react, and the fire it produces behaves differently to a conventional electrical fire in terms of heat release, off-gassing and reignition risk. Fire safety for BESS in Australia isn’t a single checkbox on a compliance form. It’s a layered set of requirements spanning product standards, siting, construction and emergency response, and getting any one layer wrong can hold up a connection approval or, worse, create a genuine site hazard.
Table of Contents
- Why BESS Fire Risk Is Different From Other Electrical Plant
- The Standards Framework: AS/NZS 5139 and How It’s Adopted
- Thermal Runaway and Why Separation Distances Matter
- Siting, Enclosures and Construction Requirements
- Fire Brigade Intervention and Emergency Planning
- State and Local Approval Pathways
- Ongoing Compliance: Maintenance, Monitoring and Documentation
- What to Do Next
- FAQ
Why BESS Fire Risk Is Different From Other Electrical Plant
Most electrical fire safety provisions in Australia were written around switchgear, transformers and cabling, where the failure modes are reasonably well understood and the fire load is largely external to the equipment. A lithium-ion BESS carries its own stored chemical energy inside every cell. Thermal runaway, an uncontrolled, self-heating chain reaction inside a damaged or abused cell, can release flammable and toxic gases, reignite after apparent suppression, and propagate cell-to-cell and rack-to-rack if the system isn’t designed to interrupt that path. This is why fire engineers and standards writers treat BESS as a distinct hazard class rather than folding it into general electrical installation rules.
The Standards Framework: AS/NZS 5139 and How It’s Adopted
The primary installation safety standard in Australia is AS/NZS 5139:2019, Electrical installations, Safety of battery systems for use with power conversion equipment. It covers general installation and safety requirements for battery systems from 1 kWh up to 200 kWh per individual BESS unit, and it excludes applications like electric vehicles, telecommunications backup and systems supporting critical continuity loads such as acute care hospitals. The Electrical Regulatory Authorities Council (ERAC), the body coordinating state and territory electrical safety regulators, issued guidance in 2021 that effectively makes compliance with AS/NZS 5139 a requirement for meeting state and territory electrical safety obligations. For systems above the standard’s capacity threshold, or for large-scale grid-connected installations, additional fire engineering and performance-based assessment typically fills the gap the standard doesn’t cover.
Thermal Runaway and Why Separation Distances Matter
A large share of BESS fire safety design comes down to preventing propagation, not preventing every possible cell fault. Separation distances between battery enclosures, between a BESS and site boundaries, and between a BESS and adjacent buildings or combustible materials are set to limit radiant heat exposure and give a credible fire safety strategy time to work. For larger installations, this is usually informed by a fire safety study that considers worst-case heat release, gas venting behaviour and the practicalities of fire brigade access, rather than a single fixed clearance figure applied uniformly across every project. Getting separation and layout right early avoids costly rework later, which is one reason it belongs inside the same design process addressed in AGILE’s guide to civil and foundation design for battery energy storage systems, where siting, access and drainage decisions are made alongside the electrical layout.
Siting, Enclosures and Construction Requirements
Enclosure and room construction requirements vary depending on whether a BESS sits outdoors in a purpose-built container, indoors in a dedicated battery room, or on a rooftop. Fire and Rescue NSW’s technical guidance on large-scale external lithium-ion BESS, and Fire Rescue Victoria’s industry battery safety material, both address enclosure separation, fire safety systems, hydrant provision and brigade intervention planning for larger installations. Where batteries are housed in an internal room, authorities having jurisdiction commonly expect a defined fire resistance level for the bounding construction, ventilation and gas detection arrangements, and clear delineation from other occupied areas of the building. These requirements sit alongside, not instead of, the National Construction Code’s general building fire safety provisions, and a compliant electrical design still needs a construction certifier or fire engineer sign-off where performance solutions are used.
Fire Brigade Intervention and Emergency Planning
Because a battery fire can’t always be extinguished with conventional means and may need to be allowed to burn out under control, fire brigade intervention strategies for BESS look different to a typical structure fire response. Site documentation typically needs to address vehicle and pump access, water supply for exposure protection rather than direct suppression, signage identifying battery hazards, and an emergency plan that names who on site is responsible for battery management system (BMS) monitoring and shutdown sequencing during an incident. For clustered or open-yard BESS installations, industry guidance also addresses segregating battery units into defined groups so that a single incident doesn’t threaten an entire site’s capacity at once. Engaging the local fire authority early, rather than treating emergency planning as a late-stage document exercise, generally produces a better outcome than trying to retrofit a response plan around a fixed layout.
State and Local Approval Pathways
Approval requirements differ across jurisdictions and depend heavily on project scale, location and whether the site is classified under a hazardous industry or dangerous goods framework. A small commercial BESS may proceed through standard building and electrical approval channels, while a large grid-scale installation can trigger development assessment, environmental authority conditions, and referral to the state fire authority as part of council or state significant development approval. This is one of the areas where documentation prepared for detailed design and for grant or planning submissions needs to be technically defensible rather than generic, a theme covered in more depth in AGILE’s article on permitting and council approvals and what detailed design documentation requires. Getting the fire safety strategy aligned with the planning pathway from the outset avoids the common scenario where a fire engineering report is commissioned only after a council or authority raises it as a gap.
Ongoing Compliance: Maintenance, Monitoring and Documentation
Fire safety compliance for a BESS doesn’t end at commissioning. Ongoing obligations typically include maintaining the BMS in an active and monitored state in accordance with the manufacturer’s requirements, periodic inspection of enclosures and fire safety systems, and keeping as-built and safety documentation current as equipment is replaced or the system is expanded. Insurers increasingly ask for evidence of this maintenance regime, and asset owners who can produce clear compliance records tend to have a much smoother experience at insurance renewal and at any subsequent development or expansion approval.
What to Do Next
Fire safety requirements for BESS touch electrical design, civil layout, building compliance and emergency planning simultaneously, which is exactly why they’re easy to under-scope if they’re treated as a separate add-on late in a project. Folding fire safety considerations into the design process from concept through to detailed drawings, rather than bolting them on afterward, is a core part of AGILE’s BESS engineering service, and it’s worth raising early with your engineering partner regardless of project scale.
FAQ
Is AS/NZS 5139 mandatory for all battery storage installations in Australia?
AS/NZS 5139:2019 applies to battery systems between 1 kWh and 200 kWh per individual BESS unit and is treated as a compliance requirement under state and territory electrical safety frameworks following 2021 guidance from the Electrical Regulatory Authorities Council. Systems outside that capacity range, or with specific applications like critical continuity power, are excluded from its scope and typically need a project-specific fire engineering approach instead.
Do residential battery systems need the same fire safety treatment as commercial or utility-scale BESS?
No. Residential systems are generally small enough to sit within AS/NZS 5139’s scope and standard electrical installation practice, whereas commercial and utility-scale BESS often require a dedicated fire safety study, separation modelling and, in many cases, direct engagement with the state fire authority because of the scale of stored energy involved.
What is thermal runaway and why does it drive so much of the design?
Thermal runaway is an uncontrolled, self-heating chain reaction inside a battery cell that can be triggered by internal faults, physical damage, overcharging or external heat exposure. Because it can propagate between cells and racks if unmanaged, a large part of BESS fire safety design is about interrupting that propagation path rather than assuming any single fire event can always be fully suppressed.
Does the National Construction Code cover BESS specifically?
The National Construction Code sets general building fire safety requirements that a BESS installation still needs to satisfy, particularly where batteries are located within or attached to a building. It works alongside, rather than instead of, BESS-specific standards and state fire authority guidance, and performance-based solutions may need fire engineer sign-off where deemed-to-satisfy provisions don’t directly address a battery installation.
When should a fire safety strategy be developed in a BESS project?
As early as possible, ideally during concept or preliminary design rather than after a layout has already been fixed. Separation distances, enclosure construction and emergency access requirements can all affect site layout and cost, and resolving them early avoids rework once detailed design or planning approval is underway.
Who assesses fire safety compliance for a BESS project?
Depending on scale and jurisdiction, this can involve the electrical designer, a fire safety engineer, the local council or state planning authority, and the relevant fire and rescue service. Larger projects typically need input from more than one of these parties, coordinated through the design and approvals process.
