UK Domestic Electrical Work: BS 7671 Guide & Overview

Quick Answer: UK domestic electrical work is governed by BS 7671:2018+A2:2022 (the 18th Edition Wiring Regulations) and Part P of the Building Regulations for England and Wales. Most circuits in a typical house sit on a metal consumer unit with RCBO protection, 32A ring finals or radials for sockets, and 6A or 10A circuits for lighting. If you carry out notifiable work without a Part P certificate or registered competent person notification, the local authority can require removal of the installation.

What this guide covers

This is the hub article for domestic electrical work in the UK. It covers what every electrician on a typical residential job needs to know in 2026: the regulatory framework, the standard circuits you will design and install, how testing and certification works, and the rules for new builds, rewires and notifiable jobs. Each section links to deeper articles for the detail.

The trade has changed a lot in the last few years. Amendment 2 to BS 7671:2018 landed in March 2022 and became mandatory for designs from 28 September 2022. It pulled in mandatory AFDDs for some installations, surge protection by default unless risk-assessed out, and tighter requirements around metal consumer units in domestic premises following the Grenfell-era fire reviews. EV charging, battery storage and heat pumps have all moved from niche to mainstream, which means electricians are doing DNO notifications and load calculations on jobs that used to be a straight consumer unit swap.

This page is aimed at jobbing domestic electricians, multi-trade builders who sub out or self-certify simple work, and project managers running rewires or extensions. If you are studying for 2391 or 2382, the linked articles go deeper on test procedures and reg references. If you are quoting a customer, this hub helps you scope the job before you walk the property.

Wiring regulations and compliance

BS 7671 is not law in itself. It becomes enforceable through the Part P Building Regulations for notifiable domestic work and through the Electricity at Work Regulations 1989 in any commercial setting. In practical terms, if you do not follow BS 7671 you cannot self-certify, and your installation will fail an EICR.

The current edition is BS 7671:2018+A2:2022. The key changes brought in by Amendment 2 are the ones that catch electricians out on site: AFDDs are now required in HMOs, care homes, student accommodation and other higher-risk premises, and a risk assessment is needed if you decide not to fit them in a standard dwelling. Surge protection devices became the default for almost all installations. Metal consumer units have been mandatory in domestic premises since Amendment 3 in 2015 and that has not changed.

Earthing arrangements decide a lot of what comes next. Most UK homes are on TN-C-S (PME) supplies with combined neutral and earth from the DNO, which brings specific bonding and disconnection requirements. Get the supply type wrong and the whole protective scheme falls apart. Read main protective bonding rules under BS 7671 Chapter 41 before you start any consumer unit work, and use the supplementary bonding decision flow for bathrooms and special locations when you are in zones.

SPD installation under BS 7671 Section 443 is now the bit most people skim and get wrong. The default is fit one. If you are not fitting one, the risk assessment needs to be written down. The Type 1, 2 and 3 SPD selection process depends on whether you have an exposed overhead line, a metallic service entry, and what equipment value you are protecting.

Common domestic circuits

A standard 3-bed semi will typically have eight to twelve final circuits. Knowing the cable sizes, breaker ratings and protection requirements for each saves you measuring twice on every job.

Socket circuits in the UK, ring final versus radial is the first decision. A 32A ring on 2.5mm² T+E covers a floor area up to 100m². A 20A radial on 2.5mm² is the simpler alternative for smaller spaces and is what most European installs default to. The socket and switch mounting heights under Part M are 450mm to 1200mm from finished floor level for new builds and material alterations, which catches a lot of electricians who fit at the old 150mm skirting height.

Lighting circuit wiring with loop-in ceiling roses versus junction boxes is mostly down to preference, but loop-in is faster and reduces hidden joints. A 6A MCB on 1.0mm² T+E covers a typical floor of lighting. Step up to 1.5mm² and a 10A MCB if you are running long cable lengths or high-load LED arrays. For controls, DALI and PIR lighting control systems under Part L are increasingly specified on extensions and new builds for energy compliance, and domestic lighting design with lux levels and LED driver matching is worth reading before you quote a kitchen rewire with downlights.

Kitchen electrical circuits with ring finals and Part P notification need careful planning. Built-in ovens under 3kW can go on the ring, but a cooker circuit on 10mm² with a 32A or 40A control unit is the norm for anything bigger. The control unit position matters: within 2m of the appliance, not behind it. Electric shower installation requires its own circuit and Part P notification in every case. A 9.5kW shower needs 10mm² on a 45A MCB, with 30mA RCD protection.

Bathroom electrical zones 0, 1 and 2 with IP rating requirements determine what fittings go where. Zone 0 is inside the bath or shower tray and needs IPX7. Zone 1 is up to 2.25m above and needs IPX4. Outside the zones is unrestricted but the whole bathroom is still a special location. Bathroom extractor fan wiring with timer and IP rating usually means an SELV fan in Zone 1 or an IPX4-rated fan above it, fed from the lighting circuit through a 3A fused spur.

For larger jobs and outbuildings, cable sizing for each circuit type with voltage drop allowance needs proper calculation, not guesswork. The BS 7671 Appendix 4 method for current capacity and voltage drop is the reference. SWA cable burial depth, gland selection and BS 7671 routing rules applies whenever you go underground, including the 600mm burial minimum under gardens and 750mm under driveways with warning tape 150mm above.

Consumer unit standards with RCBO, SPD and Amendment 2 compliance is where it all comes together. A modern board has RCBOs on every circuit (no shared RCDs), an SPD on the busbar, and the labelling required by Regulation 514. Consumer unit upgrades from plastic to metal with RCBO wiring is one of the most common notifiable jobs and is the trigger for old rewirable fuse board replacement with EICR coding.

Safety, testing and inspection

Every job ends with testing. Every test starts with safe isolation under GS38 with proving unit and lock-off. This is not optional and HSE prosecutes on it. Two-pole voltage indicator, prove on a known source, isolate, prove dead, prove indicator again. Lock off the means of isolation. Sign for it.

Electrical testing to BS 7671 with insulation resistance and RCD timing follows a fixed sequence: continuity of protective conductors, ring final continuity, insulation resistance at 500V DC, polarity, earth fault loop impedance, RCD operation. The electrical inspection checklist with BS 7671 schedule of test results gives you the structure for the certificate. Insulation resistance below 1MΩ is a fail. Earth fault loop impedance above the Zs limit for the breaker is a fail.

For EICR inspection and reporting under BS 7671 Part 6, the codes are C1 (danger present, immediate action), C2 (potentially dangerous, urgent remedial), C3 (improvement recommended) and FI (further investigation needed). A C1 or C2 makes the report unsatisfactory. Landlords have been required to hold a satisfactory EICR every five years since June 2020 under the Electrical Safety Standards in the Private Rented Sector Regulations.

Domestic smoke and heat detection is its own discipline. Smoke alarm wiring for mains, battery and RF interconnected systems needs to follow BS 5839-6 and the Building Regulations Approved Document B. Grade D2, LD2 minimum for new builds and material alterations means mains-powered with battery backup, in every escape route, every storey, plus a heat alarm in the kitchen. For commercial spaces accessed off domestic property, emergency lighting under BS 5266 with three-hour duration testing applies.

EV, solar, heat pumps and DNO notifications

This is the part of the trade that has changed most. A decade ago, an electrician finished a rewire and that was the job. Now a typical extension might pull in an EV charger, a battery, a solar array and a heat pump, each with its own notification path.

EV charger installation with DNO notification and 32A circuit is the most common addition. A 7kW charger needs a dedicated 32A circuit, Type A or Type B RCD protection depending on the unit (most modern chargers have it built in, freeing you to use a Type AC RCBO upstream), and DNO notification under EREC G100 if the total demand exceeds the supply capacity. EV charger load management with CT clamps and maximum demand control is how you fit a 7kW unit on a property with a 60A or 80A main fuse without an upgrade.

Solar PV installation under MCS with DNO G98 or G99 is the framework: G98 for inverters up to 16A per phase (notified after install), G99 for larger systems (pre-approval required). The MCS-certified solar PV and battery storage route is what unlocks SEG payments and the zero-rated VAT until March 2027. Home battery storage with DNO registration and fire safety needs careful siting: not in lofts, not in escape routes, with the BS EN 50272 ventilation and clearance rules followed.

Heat pump electrical requirements with circuit sizing and G99 notification is the newer one. A 12kW air-source heat pump on a single-phase supply will draw around 25A on a cold start, which often pushes the property over the 100A main fuse limit. Many heat pump jobs end up being supply upgrades or three-phase electrical supply installations in disguise. Quote accordingly.

New builds, rewires and notifications

Full house rewires, when one is needed and how long they take is the single biggest piece of work most domestic electricians take on. A typical 3-bed semi takes 5 to 10 working days for a full rewire, plus 2 days for plasterer-making-good. Boards on day one, first fix to second fix order, test on the final day. Notify Part P at the start, certify at the end.

Part P notification has two routes. Self-certify if you are a registered competent person (NICEIC, NAPIT, ELECSA, Stroma, Certsure). Notify the local authority Building Control before starting if you are not. Self-certify routes cost around £4 to £8 per notification through the scheme. Building Control notifications cost £200 to £500 depending on the authority.

For pre-build planning on new houses, smart home cabling pre-wire with Cat6 and coax is much easier before plasterboard. The smart home wiring guide for neutrals, Ethernet and BS EN 50173 covers what to pull in: switched-live neutrals at every switch position (often missed and required for most smart switches), Cat6 to every TV point and ceiling rose, and coax for satellite. Smart home system integration for electricians with Part P scope sits alongside CAT6 vs CAT6A cable selection for UK home networks when you are speccing the structured cabling.

Outdoor and outbuilding work is its own decision tree. Outdoor electrical installations under Part P with IP ratings and the related outdoor electrics with IP ratings, RCD and cable depth guide both apply. Electrical supply to workshops and outbuildings under BS 7671 usually means a sub-main in SWA, a small consumer unit in the outbuilding, and a separate earth electrode if the supply is TT (which most are by choice, to avoid PME issues with external metalwork).

Security and AV are increasingly part of the same job. Intruder alarm installation with Grade 2 or 3 to EN 50131 and CCTV wiring with PoE cable types and BS 5979 sit alongside PIR sensor wiring and positioning for detection zones, door entry and access control system wiring and TV aerial and satellite dish installation under UK planning rules. For temporary site installations, portable generators on site with 110V CTE is the standard.

AFDDs deserve a closer look because the reg changed and a lot of electricians still default to old habits. AFDD installation under BS 7671 with Type B and C selection, AFDD requirements under BS 7671:2018+A2:2022 and AFDD selection with Amendment 2 risk assessment all cover the same ground from slightly different angles: where mandatory, where recommended, when a written risk assessment is enough to omit them.

Common questions

Do I need Part P certification to do my own electrical work?

You can do non-notifiable work on your own home without Part P, but adding circuits, work in bathrooms, or anything outdoors is notifiable. Without a registered competent person to certify it, you must notify Building Control before starting, pay the inspection fee, and pass a third-party inspection. If you sell the house, the lack of a Part P certificate on past work shows up on searches and can block the sale.

What is the difference between an RCD and an RCBO?

An RCD only detects earth leakage and trips the supply to whatever it protects. An RCBO combines RCD function with an MCB (overcurrent protection) on a single circuit. Modern installations use one RCBO per circuit so a fault on one circuit does not knock out half the house. BS 7671:2018+A2:2022 effectively requires this approach in most domestic boards.

How often does an EICR need doing?

Rented properties need a satisfactory EICR every 5 years or at change of tenancy. Owner-occupied homes have no legal requirement, but BS 7671 recommends every 10 years for domestic. Commercial premises are typically every 5 years. Insurance and mortgage lenders increasingly ask for a recent EICR on older properties.

What size cable do I need for a 7kW EV charger?

A 7kW charger pulls 32A continuous. On a typical 10m run, 6mm² T+E or 6mm² SWA on a Type A 40A RCBO is the standard spec. Longer runs (over 15m) push you to 10mm² for voltage drop. Always do the calculation against BS 7671 Appendix 4 rather than rely on a default, because installation method (clipped direct, in conduit, buried) changes the current-carrying capacity significantly.

Can I put a socket in a bathroom?

Sockets are not permitted in Zones 0, 1 or 2 of a domestic bathroom, with the exception of shaver sockets compliant with BS EN 61558-2-5 (these are SELV and isolated). Outside the zones, a standard socket is permitted but must be RCD-protected. In a typical UK bathroom, you almost never have space outside the zones to fit one.

Where to start

If you are new to UK domestic electrical work, work through these in order:

  1. BS 7671:2018+A2:2022 wiring regulations overview is the foundation. Everything else references it.
  2. Part P Building Regulations and notifiable work tells you what you can and cannot do without certification.
  3. Safe isolation procedure under GS38 is the first thing you do on every job. Get it wrong and people die.
  4. Earthing and main protective bonding under BS 7671 underpins every protective scheme.
  5. Testing to BS 7671 with insulation resistance and RCD timing is how you certify your work.
  6. Consumer unit standards with RCBO and SPD ties the regs to a real distribution board.

Regulations and standards summary

The key UK references for domestic electrical work: