A home battery is a heavy electrical unit that has to live somewhere in or on your building. Where it goes is a safety decision, not a tidiness decision. This article explains what the UK fire safety document PAS 63100:2024 says about battery locations. It also covers the MCS battery standard, the IET Code of Practice, and what happens to a battery in a power cut.
Key Points
- PAS 63100:2024 is a publicly available specification from BSI. It was sponsored by the Department for Energy Security and Net Zero and came into effect on 31 March 2024.
- It is not a British Standard, and MCS says it has no standing in UK regulations. It is best practice, reached through the IET Code of Practice.
- Its starting position is clear. Clause 6.5.1 says that where practicable, batteries shall be installed outdoors.
- Clause 6.5.5 bans several locations outright. Lofts, roof spaces and voids are on that list.
- Bedrooms are banned. So are cupboards that open into a bedroom.
- Escape routes are banned. That covers landings, staircases and corridors, plus the stairs and lobbies of protected escape routes.
- An outdoor battery must not sit within 1 m of an escape route, a door, a window or a ventilation port.
- Indoor locations need fresh air ventilation to the outside, and fire resisting separation from the banned spaces.
- A battery in a place you rarely visit needs its own alarm. That alarm must be linked to the alarms in the rest of the house.
- A normal battery shuts down in a power cut. Backup only works if the equipment and the circuits are specified for it.
Common Misconceptions
The battery can go in the loft, it is out of the way. This is the most common request and the answer is no. Lofts, roof spaces and voids are on the banned list in PAS 63100.
PAS 63100 is the law. It is not. MCS states that PAS 63100 has no current standing in UK regulations such as Building Regulations. It is best practice that good installers follow.
A battery keeps the lights on in a power cut. Not on its own. A normal system connected to the grid has to shut down when the grid fails. ENA Engineering Recommendation G98 requires loss of mains protection to be built in and tested. G98 also puts systems designed to run as an island outside its scope, so they go through the fuller G99 route instead.
Backup means the whole house. It does not. EPS stands for Emergency Power Supply. It powers selected circuits only, and it needs a compatible inverter plus extra wiring. We confirm what it can run at survey.
Any wall will do. The unit is heavy. MIS 3012 says components shall be mounted on surfaces that are structurally sound and can carry the weight. If there is any doubt, a structural engineer is consulted.
Real-World Advice
Every solar system we have published on this site has a battery. Most use an Anker SOLIX X1 unit of 10 kWh. Two homes took a 5 kWh unit, and one in Ninfield took 20 kWh, which is our largest published. Three homes have Fox ESS units, at 5.76 kWh and 9.32 kWh.
The 20 kWh Ninfield system matters for this article. PAS 63100 sets a ceiling on how much energy you can store in one home. It is 80 kWh in a detached garage or outbuilding, or outdoors, or in an attached garage with 60 minute fire separation. It is 40 kWh everywhere else. So a normal home battery is well inside both figures, even at 20 kWh.
UK-Specific Considerations
Three documents matter in Britain, and they do different jobs.
PAS 63100:2024 is the fire safety specification for batteries in homes. BSI published it in March 2024. It covers where the battery goes, ventilation, fire separation, alarms and stored energy limits.
MCS MIS 3012 is the installation standard we work to as an MCS certified company. The 2025 issue covers battery systems up to 50 kW output. It says components shall be located so escape routes are not impeded. It also says batteries shall be located so a battery fire does not compromise protected escape routes.
The IET Code of Practice for Electrical Energy Storage Systems is the technical reference MIS 3012 tells us to read alongside it. MCS confirmed in May 2024 that the 3rd edition says PAS 63100 "should be used" for battery location. That is the link that brings PAS 63100 into MCS work.
MCS was direct about the status of all this. PAS 63100 is not written into Building Regulations, and it is not named in MIS 3012. It reaches installers as a recommendation, not a legal duty. We treat it as the rule we design to anyway.
Here is how the usual candidate spots look against PAS 63100. Every entry still depends on your building.
| Location | Verdict | Why |
|---|---|---|
| Garage, attached or detached | Usually fine | Not on the banned list in 6.5.5. It also gets the higher 80 kWh stored energy allowance, if an attached garage has 60 minute fire separation. Table 5 requires extra impact protection inside a garage. |
| Utility room | Depends | Not banned, but it is an indoor space. It needs fresh air ventilation to outside and fire resisting separation, and it must not be an escape route. |
| Understairs cupboard | Depends | Not banned by name. The hall and stairs beside it usually are, under 6.5.5(b) and 6.5.5(c). It is also a space you rarely open, so it needs its own linked alarm under 6.5.6. |
| Loft or roof space | Avoid | Banned outright by 6.5.5(g), which lists voids, roof spaces and lofts. |
| Outside wall | Usually fine | Preferred by 6.5.1. It must not sit within 1 m of an escape route, door, window or ventilation port, and must not damage the fire performance of the wall. |
| Plant room | Depends | Treated as an indoor location. Same requirements as a utility room, plus a linked alarm if it is rarely visited. |
Two more bans are worth knowing. A battery must not go within 2 m of stored flammable materials, fuel tanks or gas cylinders. It must not go in a cellar or basement with no access to the outside of the building.
The inverter is treated differently from the battery. PAS 63100 clause 7.2 allows power conversion equipment in a loft, as long as a linked smoke alarm or multi sensor alarm is fitted there. So a loft inverter can be acceptable when a loft battery is not.
People often ask about the surface behind the battery. PAS 63100 clause 6.1.1 requires the battery enclosure itself to be made of a material that will not burn, and gives steel as an example. We did not find a clause in PAS 63100 setting a rule for the wall or board behind the unit. MIS 3012 clause 3.7.6 covers strength and weight, not fire. So the manufacturer's instructions decide that point.
How we choose the spot at survey
We start outside, because PAS 63100 does. If an outside wall works, that is usually the answer. If it does not, we look at the garage next, then a utility room or plant room.
Five things then decide it. The location must not be on the banned list. It must have ventilation to outside if it is indoors. An indoor spot also needs fire resisting separation from the banned spaces. The wall or floor must carry the weight. The cable run back to the consumer unit must be sensible.
We also check what the space is used for. Fuel cans, gas bottles and paint have to be 2 m clear. Then we tell you whether an extra linked alarm is needed, and put it in the quote.
When This Isn't Right For You
- The only space you can offer is a loft, a roof space or a floor void.
- The only space is a bedroom, or a cupboard that opens into one.
- The only space is a hall, landing, staircase or other escape route.
- The only space is a cellar with no way out to the open air.
- The wall or floor cannot carry the weight and you do not want it strengthened.
Before You Spend Money
- Ask any installer where the battery will go, before you sign. Ask them to name the spot on the quote.
- If the answer is the loft, ask them to explain that against PAS 63100 clause 6.5.5(g).
- Check whether the room has ventilation to the outside. Indoor locations need it.
- Ask whether the location needs a linked smoke alarm added, and whether that is in the price.
- If you want power in a cut, say so early. EPS changes the inverter choice and the wiring.
- Ask what happens to the space around the battery. Fuel, paint and gas cylinders have to stay 2 m clear.
Frequently Asked Questions
Q: Can my battery go in the loft?
A: No. PAS 63100:2024 lists voids, roof spaces and lofts as locations where batteries shall not be installed. The inverter is treated separately and can go in a loft if a linked alarm is fitted there.
Q: Is a garage a good place for a battery?
A: Usually, yes. It is not on the banned list, and it gets the higher stored energy allowance. PAS 63100 also asks for extra protection against knocks from vehicles inside a garage.
Q: How far from a window does an outdoor battery have to be?
A: At least 1 m from the edges of doors, windows, ventilation ports and escape routes. That figure comes from PAS 63100 clause 6.5.5(f).
Q: Will my battery power the house in a power cut?
A: Only if you have specified EPS and the right inverter. Without it the system disconnects, because loss of mains protection is required by G98.
Q: Do I need a new smoke alarm?
A: Possibly. If the battery goes somewhere you rarely visit, PAS 63100 wants an alarm in that space. It must be linked to the alarms in the rest of the house.
Summary
The safe answer to "where can a home battery go" starts outside. PAS 63100:2024 asks for outdoors where that is practical, and rules out lofts, bedrooms, escape routes and sealed cellars. Garages and outside walls are the usual good answers. Utility rooms, plant rooms and understairs cupboards can work with ventilation, fire separation and an added alarm. None of it is law, but it is the standard we design to. We settle the position at survey, with the cable run, the weight and the alarms all agreed before anything is ordered.