Where Should a Home Battery Go? PAS 63100 Rules

The question that separates good battery installers from the rest

Ask three installers where your home battery should go and you will hear three answers. One measures your garage wall. One suggests the cupboard under the stairs. One says the loft, “because that’s where the inverter is going anyway”. Only one of those answers survives contact with the current safety guidance — and knowing which one puts you in a stronger position than most buyers, because battery siting stopped being a matter of preference in 2024.

PAS 63100:2024 is the British Standards Institution’s specification for protecting dwellings against fire from battery energy storage systems, sponsored by the government’s energy security department and published in March 2024. It is the reference point a competent installer now designs to, and its core logic is blunt: lithium battery fires in homes are rare, but when they happen they develop fast and produce toxic gas — so the battery must never sit where it could cut off your escape or start a fire where nobody would notice one.

This guide covers where a battery should not go, where it should, why the wrong locations keep getting proposed anyway, and how the DC-versus-AC coupling decision shapes the siting conversation.

Where a home battery should not go

PAS 63100’s exclusions read like a list of exactly the places UK installers historically put batteries:

• Not in lofts, roof spaces or ceiling voids. Lofts fail on multiple counts at once: summer temperatures well above what battery chemistry likes, difficult firefighting and rescue access, combustible structures and stored clutter, and a fire starting above the smoke alarms and the sleeping household. The loft is named specifically because it was the industry’s default easy answer.
• Not on escape routes. Hallways, landings and stairways are how you leave a burning house. A battery in flames between your bedroom and your front door is the exact scenario the standard exists to prevent.
• Not in bedrooms or spaces opening into them. Sleeping areas — including storage cupboards that open into them — are excluded. People asleep are the slowest to detect and react to a fire.
• Not in cellars or basements without external access. Below-ground spaces reachable only through the house concentrate smoke and deny firefighters a direct route in.
• Not within clearance distances of openings and flammables. Sited outdoors, a battery should stand at least 1 metre clear of doors, windows, ventilation openings and escape routes, so smoke from a failing unit cannot be drawn into the house or block the way out. Indoors and out, keep roughly 2 metres from stored fuel and flammable materials — the petrol can and the paint shelf move, not the battery.

None of this makes batteries dangerous as a category. It makes them equipment with a known, low-probability, high-consequence failure mode — which is precisely the kind of thing standards exist for.

Where a home battery should go

The compliant homes are unglamorous, and that is rather the point:

• The garage — the standout choice in most homes that have one. Cool, ventilated, solid masonry for the wall fixing, out of the living space, easy cable routes to the consumer unit in many house layouts, and space for the isolators and clearances the installation needs.
• A utility room or dedicated plant cupboard — good where the space genuinely is separate from sleeping areas and escape routes and has ventilation. This is where fire detection matters: the guidance expects detection in the space housing the battery, interlinked with the home’s alarms, so a fault announces itself early.
• An external wall — increasingly popular and well supported by current outdoor-rated units. Respect the 1 metre clearances from openings, keep the unit out of all-day direct summer sun where possible, and think about theft and vandalism exposure at the same time.
• An outbuilding — often ideal on paper; the practical questions are cable run length, voltage drop and cost of the trench.

Two physical realities shape all of these. Weight: home batteries commonly run from around 50 kg to well over 100 kg depending on capacity — wall-mounting needs solid masonry and proper fixings, and floor-standing units need a firm base. Temperature: battery performance and lifespan suffer below freezing and in high heat, so a stable, cool location is not just a safety preference, it is a payback decision. The garage that satisfies PAS 63100 also happens to be where the battery will age slowest.

What a compliant siting conversation sounds like

You can identify a good battery installer inside ten minutes of the survey, because the compliant conversation has a recognisable shape. It sounds like this:

The surveyor asks where everyone sleeps and walks the escape routes before proposing a location. They measure the garage or utility wall, check what the wall is made of, and note the distance to the consumer unit. They point out the door and window positions and explain the 1 metre rule without being asked. They look at what is stored nearby and tell you the paint and the lawnmower fuel need a new home. They talk about fire detection in the battery space. And when you ask “could it just go in the loft?” — the honest test question, worth asking even if you know the answer — they say no, explain why, and put the proposed siting in writing.

The non-compliant conversation has a shape too: it starts from the easiest cable run and works backwards to a justification. “The loft is fine, we do it all the time” was common practice before 2024. The standard exists because common practice was wrong.

If an installer proposes a location this guide rules out, ask one question: “Is that consistent with PAS 63100, and will you confirm the siting rationale in writing?” A professional will either bring the proposal into line or give you a written, reasoned justification. Anyone who waves the question away has told you how the rest of the job will go — and the siting corner-cut rarely travels alone; check their G99 paperwork discipline too, because most solar-plus-battery systems need DNO approval before energisation.

DC or AC coupling — and what it means for siting

How the battery couples to your solar system changes which locations are practical, so the siting and system-design conversations belong together.

DC-coupled (hybrid inverter). One device — a hybrid inverter — manages both the panels and the battery, with the battery connected on the DC side. It is the efficient, tidy choice when battery and solar are installed together: one conversion chain, one box on the wall, typically the best round-trip efficiency. The siting implication: the battery generally lives close to the hybrid inverter, and the inverter wants to be near the consumer unit and the incoming PV cabling. In practice the design question becomes “where can the inverter-and-battery pair go that satisfies PAS 63100?” — which is usually the garage or utility room, and pushes back against loft-sited inverters at the same time.

AC-coupled (retrofit). The battery brings its own inverter-charger and connects on the AC side, leaving the existing solar system untouched. This is the standard retrofit route, and its siting implication is freedom: the battery can go anywhere sensible on the AC side — garage, outbuilding, external wall — without rerouting the PV cabling at all. The trade-offs sit elsewhere: an extra conversion step costs a few percent of efficiency, the second inverter adds cost, and the additional inverter capacity is exactly what usually tips the property into G99 territory.

Neither coupling is “correct” — new combined installs lean DC, retrofits lean AC — but notice how often the couplings’ economics and the standard’s siting rules point at the same rooms. A hybrid inverter in a ventilated garage with the battery alongside satisfies the electrician, the standard and the battery’s own temperature preferences at once. Design decisions that agree with each other are usually the right ones. Our solar battery installation guide covers the wider design picture, and the savings calculator will show you what a battery does to your payback.

The questions buyers ask about battery siting

Is PAS 63100 actually law? No — it is a publicly available specification, not legislation. But the distinction matters less than it sounds: installers certified under the MCS scheme work to installation standards that track current best practice, insurers and building control bodies increasingly reference PAS 63100, and in any future dispute “we sited it against the published safety guidance because the cable run was shorter” is not a sentence anyone wants to defend. Treat it as the de facto rulebook, because the industry now does.

My battery was installed in the loft before 2024. Do I have to move it? The standard is not retrospective and there is no requirement to relocate existing installations. It is still worth a conversation with an MCS-certified installer at your next service point: an assessment costs little, and if the unit is ageing in a hot loft, relocation or replacement planning may make sense for lifespan reasons as much as safety ones.

Does an outdoor battery need protection from the weather? Outdoor-rated units are sealed against rain and designed for UK conditions — the real enemies are direct summer sun (heat), hard frost (performance), and siting too close to openings (the 1 metre rule). A north-facing or shaded external wall, off the ground on a proper bracket, with clearances respected, is a genuinely good home for a modern outdoor-rated unit.

Does battery siting change what I pay? Sometimes, modestly — a longer cable run, a trench to an outbuilding, or a masonry fixing kit are real line items, and a quote that itemises them is a quote you can trust. Remember the tax position while the window lasts: domestic battery installations, including retrofit battery-only installs, carry 0% VAT until 31 March 2027 under VAT Notice 708/6, after which the rate reverts to 5%. Our 2026 cost guide puts battery pricing in context.

A battery sited properly is a better battery: safer, cooler, longer-lived, and easier to sell with the house. If you want a siting assessment done to the current standard — with the location, the clearances and the G99 position all in writing — request a free quote.