The short answer
The 18th Edition of BS 7671 (the IET Wiring Regulations, in force from January 2019, with Amendment 2 from 2022) introduced several changes that directly affect consumer units in UK homes. The three most significant for domestic installations are: (1) metal (non-combustible) enclosures are now required for new consumer units in domestic premises; (2) surge protection devices (SPDs) must either be fitted or their omission formally risk-assessed for most new domestic installations; and (3) the wider adoption of RCBO boards over dual-RCD boards is now the standard design approach. Older boards installed before 2019 are not automatically illegal or required to be replaced — the 18th Edition applies to new work — but a board that predates these changes will not receive a clean periodic inspection report for the elements it lacks.
BS 7671 is updated roughly every five years. The 18th Edition, in force from January 2019, was a significant update for domestic consumer units. Here is what changed and how to read the difference between an older board and a new one.
18th Edition changes for consumer units
- In force fromJanuary 2019 (Amendment 2: 2022)
- Enclosure ruleMetal or non-combustible for new domestic CUs
- SPD ruleRequired or formally risk-assessed (Reg. 443)
- RCD/RCBOWider RCBO adoption as design default
- Retroactive requirement?No — applies to new and replacement work
What the 17th Edition board looked like — and its limitations
Most of the consumer units installed in UK homes during the 2000s and early 2010s were designed to the 17th Edition of BS 7671 (which came into force in 2008) or earlier. A typical 17th Edition consumer unit in a domestic property might have:
- A plastic enclosure — white or cream ABS, which was the industry standard at the time.
- A split-load (dual-RCD) arrangement — a main switch, two shared RCDs and MCBs per circuit. This met the 17th Edition's requirement for RCD protection on most circuits.
- No surge protection device (SPD) — the 17th Edition did not require one for most domestic installations.
- Depending on date and the specific version, varying requirements for RCD protection on different circuit types — the scope of RCD coverage increased significantly through the 17th Edition's amendments.
These boards are not dangerous in themselves — many are still giving good service — but they do not meet the full requirements that would be applied to a new installation today.
The three main 18th Edition changes for consumer units
1. Metal (non-combustible) enclosures — Regulation 421.1.201
From January 2019, new consumer units in domestic premises must be enclosed in a material meeting an 850°C glow-wire fire resistance test. In practice, this means a metal enclosure (steel) is the standard. The change was driven by fire investigation evidence: plastic enclosures can ignite and contribute to fire spread if an internal arc fault occurs. An existing plastic consumer unit is not required to be replaced retroactively, but any replacement or new installation must use a compliant enclosure.
2. Surge protection devices — Regulation 443
The 18th Edition (strengthened by Amendment 2 in 2022) requires that for most new domestic installations, a Type 2 SPD is either fitted at the consumer unit or its omission is documented in a formal risk assessment showing why it is not needed. A typical UK semi-detached house, with an overhead distribution supply and modern electronics, will usually require an SPD under this assessment. Older boards have no SPD requirement baked in; a new or replacement board should.
3. RCBO preference and RCD coverage scope
The 18th Edition and its amendments expanded the scope of circuits requiring RCD protection and moved the design default toward RCBO boards, where each circuit has its own combined breaker. Earlier editions permitted dual-RCD boards more readily; current practice and guidance favours the per-circuit RCBO arrangement. This does not mean older dual-RCD boards must be replaced, but it does mean a new board should normally be an RCBO configuration.
| Requirement | 17th Edition | 18th Edition (2019 + Amd.2 2022) |
|---|---|---|
| Enclosure | Plastic accepted | Metal (non-combustible) for new domestic installs |
| SPD | Not required for most domestic | Required or formally risk-assessed (Reg. 443) |
| RCD/RCBO type | Dual-RCD boards common default | RCBO per circuit now preferred default |
| RCD coverage scope | Most circuits (from Amd.3 2015) | Expanded / confirmed under 18th Ed |
| Existing boards | — | Not retroactively required to change |
Summary for guidance. Sources: IET BS 7671 17th and 18th Editions; Electrical Safety First guidance notes.
What this means for older boards still in homes
A consumer unit installed to the 17th Edition in, say, 2012 that is still working correctly is not automatically required to be upgraded or replaced. The 18th Edition does not apply retroactively. However:
- A periodic inspection (EICR) will assess the installation against current standards. An older board lacking an SPD, with a plastic enclosure, or with dual-RCD rather than RCBO protection is likely to receive C3 codes ('improvement recommended') for those elements. C3 codes are not failures; they flag the gap between the current installation and current new-work standards.
- If the board develops a fault that needs significant repair or replacement work, or if it needs to be extended or upgraded, the new or replacement work must meet the 18th Edition.
- If the EICR returns C2 codes (potentially dangerous), those must be addressed — but those would reflect genuine safety faults, not just the age of the board.
The practical summary: an older board in sound condition, providing its original level of protection, will typically continue to serve until a replacement is triggered by a genuine fault, a change of use, or a sale where the buyer or lender requires a current EICR.
Frequently asked questions
When did the 18th Edition of BS 7671 come into force?
The 18th Edition came into force for new electrical installations in the UK from January 2019. Amendment 2, which strengthened several requirements including surge protection, came into force in 2022. These dates apply to new work; existing installations are not automatically required to be brought up to current edition standards.
Do I have to upgrade my consumer unit to comply with the 18th Edition?
Not unless you are carrying out new installation work. The 18th Edition applies to new and replacement work, not retroactively to existing compliant installations. If your board is being replaced — for any reason — the replacement must meet the 18th Edition. An existing sound board on the 17th Edition does not have to be changed by the regulation alone.
What is an EICR and how does it relate to the 18th Edition?
An Electrical Installation Condition Report (EICR) is a periodic inspection of your existing installation by a registered electrician. The inspector assesses the installation against current standards and assigns C1 (danger present), C2 (potentially dangerous), C3 (improvement recommended) or FI (further investigation) codes to any observations. An older board may receive C3 codes for elements that do not meet 18th Edition new-work standards, but those are recommendations, not failures.
Sources & further reading
- IET — BS 7671 18th Edition wiring regulations
- Electrical Safety First — consumer unit replacement best practice guide
- NAPIT — 18th Edition guidance for electricians
Figures on this page are typical UK ranges drawn from published sources and depend on your specific property and installation. They are guidance, not a quotation.