Where can a home battery actually be installed?

Why there is a standard for this at all

A home battery is a dense block of stored energy bolted to your house for fifteen years. In normal operation it is uneventful. In abnormal operation - a manufacturing defect, physical damage, water ingress, a thermal event - the location it was installed in determines whether that becomes an inconvenience or a serious incident.

That is what AS/NZS 5139:2019 exists to govern. It is the Australian and New Zealand standard for the installation of battery energy storage systems, and Section 4 deals specifically with the pre-assembled integrated batteries used in homes - the wall-mounted units you would recognise. It sets out where they may be placed, what must be kept away from them, what the mounting surface has to be made of, and how much room has to be left around them.

It is not optional, and it rules out more locations than most homeowners expect. A quote that names a spot on your wall without anyone having assessed it is a quote written before the constraints were known.

Locations the standard allows

The standard points to garages, storage rooms, a dedicated battery room and verandas as locations that may be suitable. 'May be' is the operative phrase: suitability is decided by a risk assessment carried out before the installation is planned, not by assumption.

Where a battery is installed in a corridor, hallway or lobby, the standard requires enough clearance to get past it safely - not less than one metre - because the point of a corridor is that people can leave through it.

The location also has to allow proper access to the unit's connections, serviceable parts, and any doors or panels that need opening for installation and maintenance. A battery wedged behind a water heater in a cupboard may physically fit and still fail this test.

Locations the standard rules out

This is the part that surprises people. A pre-assembled battery must not be installed:

In habitable rooms. In a home, that means no bedrooms, living rooms, studies or similar. This single rule eliminates most of the convenient indoor locations people first suggest.

In ceiling spaces, in wall cavities, under stairways, or under access walkways. All of these are enclosed, hard to reach and hard to evacuate around.

On roofs, unless that specific installation has been deemed suitable.

In an evacuation or escape route, and not within 600 mm of any exit - the paths you would use to get out of the building have to stay clear.

Within 600 mm of a window or building ventilation opening that serves a habitable room, measured from the vertical sides. The logic is straightforward: anything a battery might emit should not have a direct path into a bedroom.

Within 600 mm of a hot water unit, air conditioner or any other appliance that is not part of the battery system, and not within 900 mm below any of those items, windows or exits.

In restricted locations as defined for switchboards in AS/NZS 3000, and not in hazardous areas - including near gas cylinders holding heavier-than-air gases and gas relief vents, because the battery is treated as a potential ignition source.

The non-combustible barrier - the rule that catches most houses

Here is the requirement that most often changes where a battery ends up in an Australian home. If a battery is mounted on, against or near a wall that has a habitable room on the other side, that wall must be a suitably non-combustible barrier. If it is not - and a standard timber-framed, plasterboard-lined wall is not - then a non-combustible barrier has to be installed between the battery and that surface.

The standard names brick or masonry block, concrete, compressed cement sheeting, and ceramic or terracotta tiles as materials accepted as suitably non-combustible. The barrier cannot have vents or perforations within the zone it is required to cover, and any penetration bigger than 5 mm has to be sealed with a fire-retardant sealant.

The barrier is not just the footprint of the battery. It has to extend roughly 600 mm beyond each vertical side of the unit, about 900 mm above it, and down to the bottom of the unit. And if the battery sits within about 300 mm of that wall - including floor-mounted units standing near it - the requirement still applies.

There is a ceiling equivalent too: where the top of the battery is within about 900 mm of the ceiling or structure above, that surface has to be suitably non-combustible for an area extending around 600 mm past the unit.

In practice this is why so many Sydney batteries end up on a brick garage wall or an external masonry wall. It is not installer preference. It is the wall behind the battery doing a job.

Clearances, and why your garage may be tighter than it looks

The standard requires enough unobstructed room on the working side of the system for safe handling, installation, removal and maintenance - not less than 600 mm, or whatever the manufacturer specifies if that is greater. Where access panels expose 230 V AC connections, that clearance increases to 900 mm.

Where multiple batteries are installed, or a battery sits alongside other equipment, spacing between them has to be accounted for as well.

This is a common reason a location that 'looks fine' does not survive assessment. A wall may have room for the battery and still not have room for someone to safely work on it in eight years' time.

Environment: heat, water, sun and vermin

Batteries have a manufacturer-specified operating temperature range, and the standard prohibits installing them where they will be exposed outside it. Beyond that, the installation has to protect the unit from water, high humidity, dust, vermin and direct sunlight.

The standard also directs that batteries should avoid localised heat sources - sunlight, generators, steam pipes, hot water systems, air conditioners, space heaters, and uninsulated walls heated by direct sun. Where an appliance blows warm air, that flow should be directed away from the battery. And a battery should not be located near combustible materials.

On ingress protection, the minimum is IP2X, and anything installed outdoors must be rated at least IP23 and appropriate for its location. Where the unit is in a damp situation, the relevant requirements of AS/NZS 3000 apply.

This is the practical reason a west-facing unshaded brick wall in Western Sydney is a worse location than it first appears, and why we look at the whole wall rather than just the spot.

Dedicated battery rooms

Where a battery is installed inside a room, the standard requires it to be positioned so that access is not obstructed by the building structure, fixtures or fittings. The room should be clean, dry and ventilated, protected from detrimental environmental conditions, and chosen to reduce the chance of material piling up around the unit or of insect or vermin infestation.

The room also has to be big enough to provide the clearances above for safe handling and access. A cupboard that fits the battery is not automatically a room that complies.

What this means when you are getting quotes

Every requirement above is decided by looking at your actual property: which rooms sit behind which walls, what those walls are made of, where the windows and vents are, where the hot water unit and air conditioner sit, how much working room there is, and how much sun the wall takes.

None of that can be determined from a phone call or a postcode. So if a quote specifies a battery location before anyone has assessed the site, either the assessment is still to come - which should be stated - or the location is a guess that may have to change later, sometimes after a deposit has been paid.

The standard also requires a risk assessment before the installation is planned, and that batteries be installed by competent persons, in line with the manufacturer's instructions and safety data. Where the system connects to the grid, AS/NZS 4777.1 applies as well, and any PV array connected to it falls under AS/NZS 5033.

Our approach is to answer the location question during design rather than on installation day. It occasionally produces an unwelcome answer - that the convenient wall will need a barrier, or that the unit has to go somewhere less tidy - but an unwelcome answer at design time is considerably better than a variation, a delay, or a non-compliant installation.

A note on what this article is

This is a plain-English summary written to help homeowners understand why battery placement is constrained. It is not a substitute for AS/NZS 5139:2019, it does not reproduce it, and it is not installation guidance - the standard itself, the manufacturer's instructions, and a licensed installer's site assessment govern any actual installation. Figures here are approximate and stated to explain the intent of the rules, not to be worked from.

If you want to know whether a particular wall in your home will work, that is a question our engineers answer during design - and one worth asking any retailer before you sign.