BS 7671 IET Wiring Regulations

BS 7671, formally Requirements for Electrical Installations, is the UK national standard for electrical installations. It is jointly published by the Institution of Engineering and Technology (IET) and BSI, and is commonly called the IET Wiring Regulations.

It governs the fixed electrical design and installation around home solar panels, batteries, EV chargepoints and heat pumps. It does not replace the product standard, network-connection process, Building Regulations or technology-specific installation standard that may also apply.

BS 7671 is authoritative but is not legislation

BS 7671 is not an Act or statutory instrument. The IET expressly warns against describing every departure from it as “illegal”.

The standard still carries considerable legal and contractual weight. The Health and Safety Executive regards compliance as a way of demonstrating conformity with relevant parts of the Electricity at Work Regulations. Building standards, contracts, certification schemes and network rules may also refer to it.

The legal route varies across the UK. In England, Approved Document P supports the electrical-safety requirement in Part P of the Building Regulations. Wales, Scotland and Northern Ireland have their own building-control arrangements. An installer must apply the rules for the property’s nation and the type of work rather than treating “Part P” as one UK-wide process.

The July 2026 edition position

BS 7671:2018 is the 18th Edition. Amendment 4 was published on 15 April 2026 and consolidated the standard as BS 7671:2018+A4:2026.

As at 22 July 2026, the preceding Amendment 3 edition remained valid until 15 October 2026. IET guidance said electrical installers could work to either edition during that transition. The selected edition should be identified on the design and certificate.

This is important for work quoted or started during 2026. “Amendment 4 has been published” and “Amendment 4 is the only valid edition” were not the same statement on the review date.

What Amendment 4 adds

The confirmed headline changes include:

• a new chapter for stationary secondary batteries;
• a new section on functional earthing and functional equipotential bonding for information and communication technology;
• a new section for power delivered over information-technology cabling; and
• a major revision of the medical-locations section.

The battery chapter matters directly to domestic storage. It covers the characteristics, selection and erection of stationary batteries and calls up PAS 63100 for battery installations in dwellings.

Amendment 4 also incorporates Amendment 3 into the consolidated text. For the exact effect on a particular PV, EV, battery or heat-pump circuit, the designer must use the published standard and current specialist guidance. A summary page cannot safely substitute for the relevant clauses.

Where home energy work fits

Different parts of BS 7671 interact with a home energy installation:

• solar PV has technology-specific requirements alongside the general rules for generating sets and parallel sources;
• an EV chargepoint is covered by the dedicated EV charging section as well as earthing, RCD, cable and circuit requirements;
• stationary battery storage is treated as an additional source of supply, including when it can operate in island mode;
• a heat pump normally uses the general rules for load assessment, circuit design, protection, isolation and verification; and
• a consumer unit and the existing installation must be suitable for the combined load and generation.

The same equipment may operate in more than one state. A battery can charge as a load, discharge as a source and supply selected circuits during an outage. Protection and isolation have to be correct in each intended state.

Existing wiring must be assessed before an addition

Adding a large electrical load or another source does not require every older circuit to be rebuilt to the latest edition. It does require the designer to establish that the existing supply, earthing, bonding, consumer unit and affected circuits are adequate for the addition and that the new work will not make the installation less safe.

An Electrical Installation Condition Report is one way to document the condition of an existing installation, but it is not automatically required before every project. The scope of any pre-installation inspection should match the proposed work and any defects found.

Common project checks include:

• supply characteristics and earthing arrangement;
• protective bonding and the condition of the service equipment;
• consumer-unit rating and available ways;
• existing maximum demand and diversity;
• prospective fault current and protective-device ratings;
• RCD type and coordination with inverter equipment;
• cable routes, voltage drop and external influences; and
• the effect of more than one source on isolation and fault current.

Electrical certification is separate from product handover

IET model forms distinguish three records:

• an Electrical Installation Certificate for a new installation or work requiring that certificate, including a new circuit;
• a Minor Electrical Installation Works Certificate for qualifying minor work that does not include a new circuit; and
• an Electrical Installation Condition Report for reporting on the condition of an existing installation.

The correct certificate records design, construction, inspection and test results. It is separate from an MCS certificate, DNO acknowledgement, product warranty or manufacturer commissioning report. A complete home-energy handover may need all of them.

BS 7671 scope and separate approvals

Compliance with the wiring standard does not itself grant permission to connect generation or export. G98, G99 and G100 deal with the distribution-network interface. MCS standards govern work certified under that scheme. Product standards and declarations cover the equipment, and Building Regulations or planning controls may apply to the building work.

The project record separates the document covering the wiring, product, grid connection, building and certified installation. “BS 7671 compliant” is not a catch-all statement for those different scopes.

Related entries

• Consumer unit capacity
• BS EN 62109 inverter safety standard
• IET EV charging code
• IET EESS code of practice
• MCS installation standards
• Building Regulations Parts L and P
• PAS 63100 domestic battery fire specification