PAS 63100 domestic battery fire specification

PAS 63100:2024 is BSI’s current specification for protecting against fire from small domestic battery energy storage systems within its stated scope. It is written for designers, installers, manufacturers and certification bodies. Its purpose is to reduce the chance that a battery becomes a source of ignition and to limit the consequences if a fire occurs.

It is more than a list of prohibited locations. It covers physical requirements for battery units, BMS, power-conversion equipment, fault management, fail-safe control and monitoring, installation location and fire protection.

The scope has firm boundaries

PAS 63100 applies to small-scale systems in domestic dwellings using stationary rechargeable batteries. BSI lists the following outside its scope:

• systems exceeding low voltage, as defined by BS 7671, on the AC or DC side;
• small secondary batteries up to 150Wh incorporated into products covered by appropriate standards;
• dwellings with more than 200m² of floor area;
• transport of batteries;
• systems using second-life batteries;
• non-battery energy storage;
• battery systems in high-risk residential buildings; and
• systems connected before the distributor’s cut-out or consumer meter.

Outside scope does not mean prohibited or safe without further work. For a dwelling above 200m², the PAS itself says its fire-safety principles may be applied but recommends consulting a fire-safety expert. Other excluded systems need the standards and risk assessment appropriate to their scale, use and building.

What compliance changes in practice

The specification requires the designer to consider the battery enclosure and protective devices, electrical interconnections, battery safety standards, BMS behaviour, fire-safe location, ventilation, detection, fire separation, warnings and verification.

It prefers outdoor placement where practicable and prohibits a defined set of sleeping, escape-route, loft and other higher-risk locations. The exact position, separation and capacity rules are covered in the related battery-placement entry.

Compliance should be demonstrated for the actual installation, not inferred from a product brochure. A conforming battery product can still be installed in a non-conforming place, and a compliant location does not correct unsuitable wiring, protection or system integration.

PAS 63100 is a standard, not an Act or regulation

PAS 63100 does not itself create a criminal offence or make a battery location “illegal”. British Standards are published for voluntary use unless legislation, a contract, certification scheme or another binding requirement calls them up.

That distinction does not make the document optional in ordinary design judgement. It records nationally agreed fire-safety practice, can be specified in an installation contract and is now referenced directly by the latest BS 7671 battery chapter.

Relationship with BS 7671 in July 2026

BS 7671:2018+A4:2026 was published on 15 April 2026 and introduced Chapter 57 for stationary secondary batteries. IET’s explanation of the amendment says Regulation 570.6.7.203 requires batteries in dwellings to be installed in accordance with PAS 63100.

As at 22 July 2026, the industry was in a six-month transition. BS 7671 Amendment 3 remained valid until 15 October 2026 and IET said installers could work to either Amendment 3 or Amendment 4 during that period. The design and certificate therefore need to identify which edition governs the work.

Once the preceding edition is withdrawn, Amendment 4 becomes the current BS 7671 route. BS 7671 is also a standard rather than legislation in its own right, but it is widely used to demonstrate electrical safety and may be made binding by law or contract in particular circumstances.

Relationship with MCS battery work

MIS 3012:2025 is mandatory for contractors certified to the MCS:2025 scheme. It covers the supply, design, installation, setting to work and commissioning of qualifying battery systems in permanent buildings up to its 50kW scope limit.

MIS 3012 says the system must be designed and installed to the latest IET Code of Practice for Electrical Energy Storage Systems. It also says the latest BS 7671 takes precedence if requirements conflict. This hierarchy matters during a standards change: an installer should not rely on an older summary when the current source document says something different.

The MCS standard does not need to repeat every PAS clause for PAS 63100 to affect an MCS installation. It is brought into the current framework through the latest IET guidance and, where Amendment 4 is used, directly through BS 7671.

Existing systems and later work

Publication of a new standard does not, by itself, make every earlier installation unlawful or require automatic removal. The relevant questions are what requirements applied when the work was designed, whether the installation remains safe and whether it has since been altered.

An extension, replacement battery or relocation is new work and should be assessed under the standards selected for that work. An inspection may also identify a present safety concern even where the original installation was acceptable at the time.

Owners should retain the design, electrical certificate, DNO documents, commissioning record, manufacturer’s instructions and any MCS certificate. Those records allow a later electrician, insurer or buyer to distinguish an evidenced design from an unsupported assurance.

Related entries

• PAS 63100 battery fire placement
• BS 7671 IET Wiring Regulations
• IET EESS code of practice
• MIS 3012 battery storage standard
• Battery location and ventilation
• Thermal runaway containment