Summary
Domestic battery storage has grown rapidly alongside solar PV, driven by falling battery costs, time-of-use export/import tariffs, and backup-power demand. Lithium-ion chemistry (predominantly LiFePO4 — lithium iron phosphate — in current domestic products, valued for its comparatively lower thermal runaway risk versus other lithium chemistries) dominates the market, but any lithium battery carries a genuine fire risk if the cell is damaged, poorly manufactured, badly installed, or manages heat and charging incorrectly.
This risk profile prompted BSI to develop PAS 63100, published in 2024 (government-sponsored) specifically in response to growing installer numbers and a small but real number of domestic battery fire incidents, at a point where no dedicated UK installation fire-safety specification existed for this product category. PAS 63100 sits alongside — not instead of — the existing product-level safety standard BS EN 62619, which covers how the cells and battery packs themselves are designed, built and tested before they ever reach an installation site.
For an installer, the practical takeaway is: check the battery product itself is certified to BS EN 62619 (a manufacturer/product-level assurance), and follow PAS 63100 for how the system is sited, ventilated, protected and connected on site (an installer-level competency and practice standard) — treating either standard as sufficient on its own misses half the risk picture.
Key Facts
- BS EN 62619 — "Secondary cells and batteries containing alkaline or other non-acid electrolytes — Safety requirements for secondary lithium cells and batteries, for use in industrial applications" — sets design, construction and test requirements for lithium-ion cells/battery packs, including thermal, electrical and mechanical abuse testing.
- PAS 63100:2024 — "Electrical installations. Protection against fire of battery energy storage systems for use in dwellings. Specification", published by BSI in 2024, setting fire-protection installation requirements covering siting, separation distances, ventilation, and installer competency for domestic battery energy storage systems.
- Chemistry matters — most current domestic battery storage products use LiFePO4 (lithium iron phosphate) chemistry, generally regarded as having a lower thermal runaway risk than other lithium-ion chemistries (e.g. NMC), though "lower risk" does not mean "no risk" — correct installation practice still matters regardless of chemistry.
- Siting is the highest-impact installation decision — PAS 63100 guidance addresses where a battery can be sited relative to escape routes, habitable rooms, and boundaries, reflecting that in a genuine thermal runaway event, the priority is limiting harm to occupants and escape routes, not necessarily saving the unit itself.
- Garage vs habitable room siting — many manufacturers and PAS 63100-aligned guidance favour siting away from principal escape routes and, where possible, away from habitable rooms — a garage or external location is often preferred over an internal hallway or under a staircase (a common historic siting choice for solar inverters that is now recognised as poor practice for battery storage specifically).
- MCS certification — MCS (Microgeneration Certification Scheme) has its own installation standard for battery storage systems, which references and aligns with PAS 63100 — MCS-certified installers should already be working to this guidance as part of their certification requirements.
- Fire and rescue service access — some guidance recommends marking the location of a battery storage system for fire and rescue service awareness, given the specific hazards (stranded energy, reignition risk) that lithium battery fires present to first responders.
- Not the same as EV battery safety standards — domestic BESS safety standards are distinct from the standards governing electric vehicle traction batteries, though both share underlying lithium-ion cell safety principles.
- Insurance implications — some insurers have begun asking specifically about battery storage installation standards (PAS 63100 compliance, installer certification) when assessing property insurance risk for homes with BESS installed — worth being aware of when advising customers.
- BS 7671 relevance — the electrical connection of a BESS (isolation, protective devices, cabling) still needs to comply with the IET Wiring Regulations in the normal way; PAS 63100 addresses siting/fire-risk practice specifically, not general electrical installation compliance, which BS 7671 continues to govern.
Quick Reference Table
Quoting an electrical job? Describe the work and squote handles the pricing.
Try squote free →| Standard | Level | Covers |
|---|---|---|
| BS EN 62619 | Product/cell | Design, construction, safety testing of lithium-ion cells and battery packs |
| PAS 63100 | Installation/system | Siting, fire risk mitigation, ventilation, installer competency for installed BESS |
| BS 7671 | Electrical installation | General wiring, isolation, protective device compliance for the connection |
| MCS (battery storage standard) | Installer certification | Installer competency scheme referencing PAS 63100 guidance |
Detailed Guidance
Two different questions, two different standards
BATTERY STORAGE SAFETY — WHICH STANDARD ANSWERS WHICH QUESTION?
------------------------------------------------------------------
"Is this battery PRODUCT safe by design?"
-> BS EN 62619 (cell/pack level testing and certification)
"Is this INSTALLATION sited and protected correctly?"
-> PAS 63100 (siting, fire risk, ventilation, competency)
"Is the electrical CONNECTION compliant?"
-> BS 7671 (Wiring Regulations)
A battery certified to BS EN 62619 installed badly (wrong location, poor ventilation, inadequate separation from escape routes) is not a safe installation overall — product certification and installation practice are separate, both necessary, assurances.
Siting decisions in practice
The core principle behind current siting guidance is limiting the consequences of a low-probability but high-severity event (thermal runaway), rather than assuming it can never happen. In practice this generally means:
- Preferring garages, external enclosures, or utility spaces over hallways, landings or spaces beneath staircases (historically common inverter/battery locations that are now considered poor practice specifically for battery storage).
- Maintaining clear separation from escape routes so that, in the event of a fire, occupants' ability to exit the property isn't compromised by the battery's location.
- Following the manufacturer's stated clearance/ventilation requirements exactly, since thermal management design varies between products.
- Considering total installed battery capacity in a single location — larger installed capacity generally warrants more conservative siting decisions.
Where this fits with wider solar/battery installation practice
Battery storage retrofits are frequently added to an existing solar PV installation, sometimes by a different installer to the original PV installer. PAS 63100 compliance and BS EN 62619 product certification should be checked independently at the point of the battery addition — an existing, compliant PV installation doesn't imply anything about the battery addition's compliance, since these are separate systems with separate standards.
Frequently Asked Questions
Is BS EN 62619 a UK-specific standard?
No — it's a European/international standard (EN-adopted) covering lithium-ion cell and battery safety more broadly, used across industrial and consumer battery applications, not written specifically for domestic UK solar-battery installations. PAS 63100, by contrast, is a UK-specific (BSI, government-sponsored) specification written specifically for fire protection in the installation of battery energy storage systems in UK dwellings.
Does PAS 63100 replace BS 7671 for the electrical connection?
No. PAS 63100 addresses siting, fire risk and installer competency specifically for the energy storage system; the general electrical installation (isolation, cabling, protective devices) still needs to comply with BS 7671 in the normal way. The two standards are complementary, not alternatives.
Why is siting given so much emphasis for battery storage compared with, say, a solar inverter?
Lithium-ion batteries carry a specific fire risk (thermal runaway) that most other domestic electrical equipment doesn't, including a small chance of a fire that's difficult to extinguish and can reignite. This is why siting guidance for batteries is more conservative than for equipment like inverters — the consequence profile of a rare failure is more severe, so the guidance prioritises keeping any such event away from escape routes and habitable spaces.
Do I need a specific certification to install battery storage systems?
There's no single mandatory licence in the way Gas Safe governs gas work, but MCS certification (for schemes requiring it, e.g. for certain grant eligibility) has its own installation standard for battery storage that references PAS 63100, and reputable manufacturers generally require installer training/accreditation before supplying products for warranty-backed installation. Always confirm the specific manufacturer's and any relevant scheme's installer requirements.
Regulations & Standards
BS EN 62619 — safety requirements for secondary lithium cells and batteries (cell/pack level).
PAS 63100:2024 — specification for protection against fire of battery energy storage systems for use in dwellings (installation/system level).
BS 7671 (IET Wiring Regulations) — general electrical installation compliance for the connection.
MCS battery storage installation standard — installer certification scheme requirements referencing PAS 63100.
BSI — PAS 63100:2024 — the installation fire-protection specification.
BSI — BS EN 62619 — the cell/battery pack safety standard.
MCS — Battery storage certification — installer certification requirements referencing PAS 63100.
National Fire Chiefs Council — battery energy storage system safety guidance — fire service perspective on BESS risk and siting.
battery storage — general domestic battery storage technical guide
home battery storage installation pricing guide — pricing context for domestic battery storage installation
smart export guarantee explained — related solar/battery revenue context
smart home battery storage integration — smart-home integration considerations for battery systems