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Batteries · For traders

Battery siting checklist

Short answer

Outdoors wherever practicable. Indoors only where PAS 63100 does not exclude it, with ventilation to outside and REI 30 separation from excluded spaces. Excluded: bedrooms, escape-route landings, stairs and corridors, cupboards opening into bedrooms, lofts and voids, cellars without outside access, within 2 m of fuels, and outdoors within 1 m of doors, windows, vents or escape routes.

Last checked 24 September 2026 · 4 sources

What should I know before deciding?

cl.6.5.1 outdoors preferred; detached outbuilding (or REI 120 separated) counts as outdoors. cl.6.5.5 list (a)-(i) is the full exclusion list. Living rooms, kitchens and under-stair cupboards are not named, but need REI 30 separation from escape routes plus ventilation to outdoors (6.5.3-6.5.4), so rarely workable. Garages/driveways: battery IK10, PCE IK08 or barriers (6.6/7.3). Detection interlinked to BS 5839-6 in rarely visited spaces (6.5.6).

How much battery capacity is allowed per unit and per home under PAS 63100?

No single battery enclosure may hold more than 20 kWh (cl.6.1.3). Per dwelling house the total is 80 kWh if the batteries are outdoors, in a detached garage or outbuilding, or in an attached one separated by REI 60 construction; in every other case the limit is 40 kWh (cl.6.5.7).

20 kWh is per enclosure: three 13.5 kWh Powerwalls (40.5 kWh) pass per unit but exceed the 40 kWh total, so they must be outdoors, in a detached outbuilding or in an REI 60 attached garage. Count all units in the dwelling, including expansions added later. Commercial-scale '150 kWh of Sigen' style banks exceed 80 kWh and are outside PAS domestic limits - need fire-engineering / non-dwelling approach.

How far must an outdoor battery be from doors, windows and vents?

At least 1 m from escape routes, doors, windows and ventilation ports, measured for ground- or wall-mounted outdoor units (PAS 63100 cl.6.5.5 f). Wall mounting must not compromise the external wall's fire performance: fire-stop penetrations and fit cavity barriers. Near driveways, parking or highway walls, batteries need IK10 and inverters IK08 or barriers.

Indoor ventilation outlets also need edges >=1 m from doors, windows and other vent ports (6.5.4). Keep >=2 m from oil tanks, LPG cylinders and stored flammables. External mounting may need planning or building control checks (6.5.2 Note).

Does an indoor battery need a 60-minute fire-rated room?

Not as a general rule. PAS 63100 requires REI 30 (30-minute) fire-resisting separation between an indoor battery location and the excluded spaces such as escape routes and bedrooms, with fire-stopped penetrations. REI 60 only applies to an attached garage or outbuilding to use the 80 kWh cap, and to battery enclosures with 4-8 cal/cm2 arc-flash energy.

cl.6.5.3 REI 30 to BS EN 13501 (30 min BS 476). cl.6.5.7(a)(3) REI 60 attached garage for 80 kWh. cl.6.3.2 Table 2 REI 60 enclosure for 4-8 cal/cm2.

What labels and notices does a home battery need?

PAS 63100 requires BS 7671 warning notices plus a battery instruction notice (PV+battery or battery-only symbol, to BS EN IEC/IEEE 82079-1) at the origin, at the meter if remote, and at the consumer unit fed by the inverter. MIS 3012 adds IET CoP Appendix C labels: C.2 and C.5 always, C.3 for DC-coupled systems.

Dual-supply labels at origin and isolators. Emergency shutdown procedure visible. Labels must be durable (MIS 3012 App A).

What to do next

Record the design assumptions, protection settings and commissioning results. Keep the DNO approval and final settings with the handover pack.

Sources

Last checked: 24 September 2026