Interest in home battery storage has grown considerably as more households look to get more from their solar panels and take advantage of cheap overnight tariffs. Along with that growth has come a reasonable question: how safe are these systems, and what standards govern how they’re installed?
The honest answer is that battery storage, installed correctly, is safe. But “installed correctly” is doing a lot of work in that sentence. In March 2024, the British Standards Institution published PAS 63100:2024 — a specification focused specifically on protecting homes against fire from battery energy storage systems. Here’s what it covers and what it means if you’re considering a battery installation.
What is PAS 63100:2024?
PAS 63100:2024 is titled “Electrical installations — Protection against fire of battery energy storage systems for use in dwellings”. It was developed by Electrical Safety First alongside BSI, with input from organisations including NICEIC, NAPIT, ECA and SELECT. It sits alongside BS 7671 (the wiring regulations) and BS 7671:2018+A4:2026, which introduced updated requirements for battery storage circuits.
Where BS 7671 covers the electrical installation — the wiring, protective devices, earthing — PAS 63100 focuses specifically on fire risk. Its aim is to reduce the likelihood of a battery becoming a source of ignition, and to limit the consequences if a fire does occur.
Are home batteries actually a fire risk?
Battery fires are uncommon, but they can be serious when they occur. The main concern with lithium-ion batteries is thermal runaway — a chain reaction in the cells that generates intense heat and can be very difficult to extinguish. Unlike a conventional electrical fire, a battery in thermal runaway can reignite after it appears to have been put out.
That said, the risk needs to be kept in proportion. The batteries used in reputable home energy storage systems are designed with multiple layers of protection against this — overcharge protection, temperature monitoring, fault detection. A well-specified system, installed in the right location by a competent installer, presents a very low risk. The purpose of PAS 63100 is to make sure that “right location” and “competent installer” are clearly defined, rather than left to chance.
Where batteries can and cannot be installed
The most significant part of PAS 63100 for most homeowners is the list of locations where batteries should not be installed. These include:
- Bedrooms or any room used for sleeping
- Lofts, roof spaces and voids
- Staircases, hallways and escape routes
- Cupboards that open directly into a bedroom
- Basements without direct access to the outside
- Within two metres of flammable materials or fuel storage
The loft restriction is particularly relevant. A significant number of battery installations — particularly older ones — were placed in loft spaces for convenience. PAS 63100 advises against this because of the difficulty in accessing the space quickly in an emergency, and because a fire in a loft has a direct path into the roof structure.
The preferred location is outdoors wherever practical. A battery installed in a detached outbuilding, external enclosure, or suitably fire-separated garage presents a lower risk to the dwelling. Where indoor installation is necessary, the standard sets out fire safety measures to compensate: fire-resisting separation from occupied areas, ventilation to external air, fire stopping around cable penetrations, and appropriate fire detection.
Maximum storage capacity
PAS 63100 also introduces limits on how much stored energy can be installed in different locations. The limits are:
- 80kWh when installed outdoors, in a detached outbuilding, or within a suitably fire-separated garage
- 40kWh in all other indoor scenarios
For most domestic installations — a single 5kWh to 15kWh battery — this isn’t a constraint in practice. But for larger or stacked systems it’s a consideration, and it ties battery sizing to the installation location.
Fire detection requirements
Where a battery is installed, the dwelling should have an appropriate fire detection and alarm system in place — at minimum Grade D2, Category LD2. A single battery-powered smoke alarm is not sufficient.
Where the battery or its associated inverter is located in an infrequently visited space — a store cupboard or plant room, for example — a smoke alarm or multi-sensor detector must be installed there and linked to the rest of the alarm system in the property. The principle is that a fault developing in an unoccupied space should still trigger an alert.
Battery management and monitoring
Every battery installation must include a Battery Management and Monitoring System (BMMS). This is the built-in system that monitors the state of the battery, detects abnormal operating conditions, and provides warnings if something is wrong. It should give visual warnings for dangerous conditions and audible warnings where appropriate.
Most reputable battery systems — SigEnergy, Tesla Powerwall, FoxEss, and others — include BMMS functionality as standard. It’s one reason that buying a recognised system from an established manufacturer matters: the safety architecture is built in, not bolted on.
Is PAS 63100:2024 mandatory?
Strictly speaking, PAS 63100 is guidance rather than legislation. It does not carry the same legal force as, for example, the Building Regulations. However, MCS-certified installers are required to follow it as part of their certification scheme, which means any battery installation carried out by an MCS installer and registered under MCS must comply. Many insurers are also beginning to reference it.
In practice, if you’re having a battery installed by a qualified, certified installer, you should expect PAS 63100 to be followed as a matter of course. If an installer isn’t aware of it or is proposing to put a battery in a loft without any additional fire safety measures, that’s a sign to look elsewhere.
What to ask your installer
When getting quotes for battery storage, a few questions are worth asking:
- Where are you proposing to install the battery, and why is that location compliant with PAS 63100?
- What fire detection is currently in the property, and is it sufficient for a battery installation?
- Is the installation being registered under MCS and notified under Building Regulations Part P?
- What documentation will I receive on completion?
A competent installer should be able to answer all of these without hesitation. The paperwork matters too: you should receive an Electrical Installation Certificate, an MCS certificate, and documentation confirming the installation is compliant with PAS 63100.
If you’re in Bristol or South Gloucestershire and want to talk through battery storage for your home, get in touch. We install battery storage systems to the current standards and can advise on the right system and location for your property.
