Battery storage
BS 7671 Amendment 4: New Battery Siting Rules for UK Homes
The April 2026 amendment to the UK wiring regulations added a full chapter on stationary battery storage. Lofts, bedrooms, hallways and stairwells are now banned locations. If you are planning a battery installation, or if you already have one in the wrong place, here is what you need to know.
Helpful video reference. eFIXX ENERGY’s explainer “UK Government Just Made Home Battery Installations Much Harder” walks through what Amendment 4 means for battery siting in plain terms.
Installer transition date: 15 October 2026. BS 7671 Amendment 4 came into force on 15 April 2026. Installers have until 15 October 2026 to work to the new rules. Any MCS-certified battery installation after that date must comply with the Amendment 4 siting requirements. Work that was designed and contracted before that date under the previous rules is not automatically invalid, but any new installation must meet the new standard.
1. What changed in April 2026
Amendment 4 to BS 7671:2018 (the 18th Edition of the IET Wiring Regulations) added a dedicated new section covering stationary secondary batteries, meaning home energy storage systems of the kind paired with solar. Before Amendment 4, battery siting guidance was spread across several documents and not uniformly enforced. Amendment 4 consolidates it into a single set of requirements.
The core change for homeowners is straightforward: certain rooms are now explicitly prohibited as battery locations because a fire starting there could trap occupants before they reach an exit.
2. Banned locations under Amendment 4
The following locations are not permitted under Amendment 4:
- Lofts and roof spaces. A fire in the loft cuts off the upper-floor escape route. Lofts were already prohibited under PAS 63100:2024, and Amendment 4 reinforces this in the wiring regulations.
- Bedrooms and sleeping areas. Occupants are at most risk during the hours they are asleep and cannot respond quickly to an alarm.
- Hallways and stairwells. These are the primary escape routes in most homes. A battery fire here would block the exit.
- Small internal cupboards that form part of an escape route. Under-stair storage and similar cupboards in the line of escape are also prohibited.
This list matches and extends the guidance already in PAS 63100:2024, but it now carries the weight of the wiring regulations rather than just a product standard.
3. Compliant locations
The following locations are generally acceptable under Amendment 4, subject to the specific installation meeting the ventilation, clearance, and fire-separation requirements:
Where a battery can go
- Garage (attached or detached): the most common choice for UK installations. Must have a fire-rated door or wall separating it from the living space where the battery is on the shared wall.
- Outbuilding: a garden office, workshop or similar detached structure. Good thermal conditions if insulated, and remote from the house in the event of a fire.
- Utility room: acceptable if there is adequate fire separation from the hallway and rest of the house. Check with your installer whether the partition meets the required fire rating.
- External wall-mount enclosure: purpose-built weatherproof enclosures mounted on an external wall are a growing option, particularly for homes with no suitable indoor space.
- Ground floor non-escape rooms: a dedicated plant room or meter cupboard at ground floor level, provided it does not form part of an escape route, may also be acceptable. Your MCS installer can confirm.
4. How Amendment 4 relates to PAS 63100
PAS 63100:2024 (the British Standard for battery energy storage systems) covers the physical safety of the battery unit itself: the chemistry, enclosure rating, clearance distances from combustibles, ventilation needs, and how the battery is fixed in place. It also includes siting restrictions (no lofts, no escape routes), but as a product and installation standard rather than wiring regulation.
BS 7671 Amendment 4 sits alongside PAS 63100 rather than replacing it. An MCS-certified battery installation must meet both. Where the two overlap (the loft and escape-route bans, for instance), Amendment 4 now makes those rules part of the certified electrical installation rather than just a product recommendation.
In practice, if your MCS-certified installer followed PAS 63100:2024 correctly when fitting your battery, you are very likely already compliant with Amendment 4 on location. The bigger change is for any older installations or any installer who was not following PAS 63100 fully.
5. What this means if you already have a battery
Amendment 4 applies to new installations, not retrospectively to systems fitted before it came into force. If your battery was installed legally before April 2026 in a location that Amendment 4 would now prohibit (for example, in a loft under the previous guidance), you are not automatically required to move it. However, your home insurer may have views on this, and if you ever sell the property the buyer’s solicitor may flag it. Worth discussing with your installer or surveyor.
Frequently Asked Questions
Can I install a home battery in my loft?
No. BS 7671 Amendment 4 explicitly prohibits battery storage in lofts. A loft fire would cut off the escape route for occupants on upper floors. The same rule applies to bedrooms, hallways, and stairwells. This was already best practice under PAS 63100:2024, but Amendment 4 makes it a wiring regulation requirement.
Where can I put a home battery under the new rules?
Garages, outbuildings, utility rooms with adequate fire-rated separation, and dedicated external wall-mount enclosures are all compliant. The location must have a non-combustible floor or backing, adequate ventilation, and enough clearance from anything flammable. Your MCS-certified installer will confirm the specific requirements for your chosen location.
When do the new rules apply?
Amendment 4 came into force on 15 April 2026. Installers have until 15 October 2026 to transition fully to the new rules. Any MCS-certified installation after that date must comply with the Amendment 4 siting requirements.
Get an MCS battery installation quote PAS 63100 battery siting guide