Regulation

BS 7671 Amendment 4 2026 — Solar PV and Battery Storage Guide

Last updated 2026-06-13 · For UK solar and battery engineers

Key dates

Published: 15 April 2026, jointly by the IET and BSI. Formal designation: BS 7671:2018+A4:2026.

Transition period: 15 April to 15 October 2026. Both Amendment 3 and Amendment 4 are valid for new work during this window.

Mandatory date: 15 October 2026. After this date all new electrical installation work must be certified against Amendment 4. The previous edition is formally withdrawn.

Not retrospective: Existing compliant installations do not need to be retrofitted. Any addition or alteration after 15 October 2026 must comply with Amendment 4 for the parts being added or altered.

New Chapter 57 — Battery storage installations

This is the most significant change in Amendment 4 for solar and battery installers. Chapter 57 (the 570.x regulation series) covers stationary battery systems for permanent installation, including domestic batteries paired with solar PV (Tesla Powerwall, Sigenergy, FoxESS, SolaX, SolarEdge Home Battery, and others).

Loft installations are prohibited

Battery storage cannot be installed in a loft.Chapter 57 formally prohibits this. The reasons: extreme summer temperatures, poor ventilation, combustible building materials, restricted emergency access, and location above sleeping areas. This formalises what responsible installers were already doing, but it now carries regulatory weight as a hard prohibition.

Other prohibited locations

Escape routes, corridors, and stairwells
Cellars and basements with no direct external access
Within 1 metre of windows, doors, or ventilation openings on external installations
Within 2 metres of stored flammable materials or fuel tanks

Acceptable locations

Garages with appropriate fire separation, utility rooms, dedicated plant rooms, and external enclosures meeting the ventilation and clearance requirements.

Thermal runaway provisions

Chapter 57 requires a battery management system with temperature monitoring and automatic disconnection on fault. For domestic dwellings, Regulation 570.6.7.203 references PAS 63100:2024 (Protection Against Fire of Battery Energy Storage Systems). Chapter 57 and PAS 63100 work together for domestic BESS — they do not replace each other.

Safe isolation

Battery systems present live DC voltage even after the AC supply is switched off. Chapter 57 codifies isolation sequences and labelling obligations. Battery installations must be labelled with: nominal voltage, capacity, chemistry, and isolation points. The Electrical Installation Certificate must capture battery system details.

Protective devices

Devices must be rated for two-way energy flow. Standard AC overcurrent devices are not always rated for DC or bidirectional operation. Amendment 4 makes the selection criteria explicit.

Chapter 712 — Solar PV changes

Chapter 712 is updated in Amendment 4. The changes are refinements rather than a rewrite:

Isolation requirements for the PV source (DC side) and AC output are more explicitly stated, including accessibility and labelling standards
Protective device requirements updated to address bidirectional energy flow, relevant where battery storage is DC-coupled alongside PV
Circuit identification and labelling obligations for grid-tied solar circuits are clarified

The fundamental connection requirements in Section 551 (how a generator connects to a domestic installation) are unchanged by Amendment 4.

RCD selection: Amendment 4 tightens guidance on RCD types in installations with inverter-based generation. Inverters typically produce DC residual fault current that Type A RCDs cannot reliably detect. Solar PV and battery inverters almost always require Type B RCDs or equivalent. Amendment 4 makes this explicit where previously it relied on installer interpretation.

Chapter 722 — EV charging and V2G/V2H

Chapter 722 is updated to address bidirectional charging. Protective devices on EV circuits that can export must be rated for two-way current. DC fault detection requirements are specified for Mode 3 connections. BESS disconnection requirements are included for co-installed solar-battery-EV charger configurations.

For solar installers: the regulatory relationship between Chapter 57 (battery), Chapter 712 (PV), and Chapter 722 (EV) is now formally codified for the first time, giving designers a framework for integrated energy systems.

What about plug-in solar?

Amendment 4 did not legalise plug-in solar via a standard 13A socket.Despite some media coverage linking the two, Section 551 (generator connection requirements) is unchanged by Amendment 4. Connecting a plug-in solar kit via a standard BS 1363 socket is not compliant with BS 7671.

What is in progress separately: the government announced in March 2026 an intention to make plug-in solar available to consumers. A BSI product standard and a G98 amendment are required. Neither was complete as of June 2026. A future amendment to BS 7671 may follow once those steps complete.

How to get Amendment 4

Purchase from the IET bookshop at electrical.theiet.org. The standard must be purchased.

Update training: City and Guilds qualification 2382-26 covers Amendment 4 (replacing 2382-22 from 16 October 2026). EAL is also issuing a replacement Level 3 Award. Update courses are one day for existing 18th Edition holders.

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