When did the 18th Edition come into effect?

BS 7671:2018 (18th Edition) was published on 2 July 2018 and came into effect on 1 January 2019. From that date, all new electrical installations and alterations must comply with the 18th Edition. Amendment 1 was published in February 2020 and Amendment 2 in March 2022. The current version is BS 7671:2018 + A2:2022. A new edition is expected in due course but the 18th Edition remains current as of 2026.

Do I need AFDDs in domestic installations?

BS 7671:2018 Regulation 421.1.7 recommends (but does not mandate for all installations) Arc Fault Detection Devices (AFDDs) to BS EN 62606. Amendment 2 strengthened the recommendation for AFDDs in locations with sleeping accommodation, premises with combustible construction (timber frame), and locations with fire risk. While not yet a mandatory requirement for all circuits, AFDDs are increasingly specified by designers and some building control bodies. They detect series and parallel arc faults that RCDs and MCBs cannot.

When is surge protection (SPD) required?

BS 7671:2018 Regulation 443 requires a risk assessment for surge protection (SPD). Under Amendment 2:2022, SPDs are effectively required in most domestic installations because the consequences of an overvoltage include risk of injury (e.g., loss of smoke/CO alarms, medical equipment) or significant economic loss. A Type 2 SPD at the consumer unit is the minimum requirement. Type 1+2 combined SPDs are needed where the supply is overhead or where lightning risk is elevated.

What changed with consumer unit requirements?

Since January 2016 (Amendment 3 to the 17th Edition, carried forward to the 18th), all consumer units and similar switchgear assemblies in domestic premises must comply with BS EN 61439-3 and be constructed of non-combustible material (metal or metal-clad). This was introduced following fires caused by overheating connections in plastic consumer units. All new consumer units installed in domestic premises must be metal.

What are the RCD requirements in the 18th Edition?

The 18th Edition significantly expanded RCD requirements. Regulation 411.3.3 requires 30mA RCD protection for all socket outlets up to 32A, all circuits in bathrooms, cables concealed in walls at less than 50mm depth (without mechanical protection), and mobile equipment up to 32A used outdoors. The result is that virtually all domestic circuits now require RCD protection. Split-load boards or RCBO-per-circuit configurations are the standard approach.

BS 7671 18th Edition Changes — Key Updates

Major Changes from 17th to 18th Edition

Topic	17th Edition	18th Edition (inc. Amendment 2)
Consumer units	Metal required from Amd 3 (2015)	Metal required — carried forward (Reg 421.1.201)
RCD protection	Required for sockets, bathrooms, outdoor	Expanded — virtually all domestic circuits (Reg 411.3.3)
AFDDs	Not mentioned	Recommended for sleeping, combustible, fire risk (Reg 421.1.7)
Surge protection (SPD)	Guidance only (Reg 443)	Risk assessment required — effectively mandatory in most cases (Reg 443)
EV charging	Basic guidance	Dedicated Section 722 — PME earthing, cable sizing, load management
Energy efficiency	Not addressed	New Part 8 — energy efficiency in electrical installations
Prosumer installations	Basic Section 712	Updated Section 712 — solar PV, battery storage, grid interaction
Wiring systems	Cables in walls <50mm need RCD	Same requirement with clearer definition of zones (Reg 522.6.202)

Amendment 2:2022 Key Changes

Change	Regulation	Impact
SPD risk assessment simplified	443.4	SPDs now required in most installations
AFDD recommendation strengthened	421.1.7	Stronger recommendation for specified premises
EV charging clarifications	Section 722	Load management, PME earthing options, cable sizing
Battery storage systems	Section 712	New requirements for domestic battery installations
Cable sizing tables updated	Appendix 4	Some current ratings revised
Temporary installations	Section 740	Updated guidance for temporary event installations

New Section 722 — EV Charging

Dedicated circuit required — not shared with other loads
PME earthing: earth rod required unless chargepoint has protective measures (PEN fault detection)
Minimum 30mA Type A or Type B RCD (depending on chargepoint DC fault protection)
Cable sizing for continuous load (apply 1.0 factor — no diversity for single chargepoint)
Load management systems (smart charging) recognised for multiple chargepoints
SPD required at the chargepoint circuit origin

New Part 8 — Energy Efficiency

Designers must consider energy efficiency in the selection of equipment and wiring systems
Power factor correction where appropriate
Minimising standby power consumption
Efficient lighting design and controls
Metering and monitoring of energy consumption

Note: This is a summary of key changes for reference purposes. Always consult the full text of BS 7671:2018 + Amendment 2:2022 for definitive requirements. The IET On-Site Guide and Guidance Notes provide additional interpretation and practical guidance.

See the BS 7671 Domestic Circuit Guide, the Wire Colour Codes, the Cable Ampacity Table, and the UK Cable Sizes reference.

BS 7671 18th Edition Changes — Key Updates

Major Changes from 17th to 18th Edition

Amendment 2:2022 Key Changes

New Section 722 — EV Charging

New Part 8 — Energy Efficiency

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