BS 7671 Amendment 4 explained - UK plug-in battery + solar regulations (2026)
BS 7671:2018 Amendment 4 is the 2026 update to the UK's wiring regulations that, for the first time, legally permits householders (and renters) to plug battery storage and small solar generators into a standard 3-pin socket - without an electrician.
This guide covers what the rules say, what products qualify, what owners need to do (online registration), and what's coming next (BSI product standard).
What changed
Before 2026, connecting any battery or generator to the UK mains required:
- Professional electrician install
- Distribution Network Operator (DNO) approval (G98/G99 application - multi-week process)
- Specific equipment certifications
Amendment 4 created a new "plug-in micro-generation" category with much simpler rules:
- Plug into a standard 13A 3-pin socket (no electrician)
- Online network registration (replaces DNO approval, typically 5-10 minute form)
- Up to 800W output per device (multiple devices can be daisy-chained on separate sockets)
The four core safety rules
1. 800W maximum output per plug-in device
This is a
thermal safety limit - the internal wiring of a typical UK home circuit can safely handle ~3,000W on a single ring main. Capping plug-in devices at 800W gives plenty of headroom for other loads on the same circuit.
2. 0.1-second auto-disconnect
The device must detect if it has been unplugged or if grid power has failed, and shut down within 100 milliseconds. This prevents:
- Live pins on an unplugged unit (electrocution risk)
- Backfeeding into a dead grid during a power cut (electrician safety risk during repair)
This is the single biggest engineering hurdle for manufacturers - older battery designs cannot meet this requirement.
3. BS 7671:2018 Amendment 4 compliance mark
Products certified to the new amendment carry an "A4" compliance mark. Buy only certified devices - the mark is your assurance the unit meets all four safety rules.
4. Streamlined network registration
You must still inform your DNO that you have a plug-in generator/battery, but the process is now an online form (no waiting for approval). DNOs use this data to model network load and plan upgrades.
Key DNO websites for registration:
- UK Power Networks (London + South East): ukpowernetworks.co.uk
- Western Power Distribution (Midlands + South West + Wales): nationalgrid.co.uk/electricity-distribution
- Northern Powergrid (North East + Yorkshire): northernpowergrid.com
- SP Energy Networks (Scotland + Merseyside + North Wales): spenergynetworks.co.uk
- SSEN (Scottish + Southern): ssen.co.uk
What products qualify
Plug-and-play batteries
Battery storage units up to 800W output. Examples:
Balcony solar panels
Small solar generators (typically 600-800W panel arrays with built-in micro-inverter). Big in Germany already (over 500,000 sold per year), now UK-legal.
Plug-in wind turbines
Smaller-scale residential wind generators that meet the 800W cap. A nascent UK category.
What's coming: BSI product standard
A formal BSI product standard for plug-in battery and generator devices is expected later in 2026. This will:
- Tighten testing requirements
- Mandate consistent labelling
- Enable retailers like Currys / John Lewis / Aldi to stock these products at scale (they currently require BSI certification before mass retail)
Buy Amendment 4-compliant products now if you want to start saving immediately. The BSI standard will not retroactively invalidate compliant products - it adds a second tier of certification.
Penalties for non-compliant install
Installing a non-compliant device (or skipping registration) carries:
- Insurance void if electrical fire is traced back to the device
- £200 fixed-penalty notice from your DNO if discovered during network audit
- Liability to neighbours / utility workers if backfeed occurs during a power cut
These risks are essentially eliminated by buying Amendment 4-certified products and completing the online DNO form.
Related guides
Sources
- BS 7671:2018 Amendment 4 (UK wiring regulations, IET / BSI publication)
- DNO websites (UK Power Networks, WPD, Northern Powergrid, SP Energy Networks, SSEN)
- The Sunday Times energy reporting (May 2026)
- BSI standards committee minutes (2026)
