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Consumer unit vs fuseboard: the terminology and the swap

'Fusebox', 'fuseboard' and 'consumer unit' get used interchangeably in conversation. They are not the same thing in BS 7671 terms. What each one means, and when the swap becomes mandatory under Amendment 2:2022.

The terminology matters because Building Regulations, EICR coding and BS 7671 refer to specific device types. A homeowner saying "my fusebox is old" and an electrician hearing "you have a fuseboard" have not necessarily agreed on the same thing.

The three terms, defined

Fusebox is the informal, everyday word. It covers any consumer-side distribution board regardless of type. BS 7671 does not use it.

Fuseboard is the correct technical term for a board that uses rewireable fuses (the ceramic-carrier type, not modern cartridge fuses). These are the pre-1970s installations still occasionally found in unmodernised Canterbury properties. They have no MCB protection, no RCD protection, and rewiring a blown fuse requires unscrewing the carrier, replacing the wire, and re-inserting - a job intended for the owner but easy to get wrong.

Consumer unit is the correct BS 7671 term for a modern distribution board that uses MCBs (miniature circuit breakers), RCDs (residual current devices) or RCBOs (combined MCB + RCD in one module). Every domestic distribution board installed since the early 1990s is a consumer unit, not a fuseboard.

Colloquially all three terms get used for any-domestic-distribution-board. Technically only the current-standard board is a consumer unit.

The evolution

Domestic distribution boards have gone through five broad generations:

1. Wooden-backed rewireable fuseboard. Pre-1960s. Ceramic fuse-carriers, no MCB, no RCD. Category C1 on modern EICR.
2. Wylex Standard MCB board. 1970s–80s. MCBs replaced ceramic fuses, but no RCD. Category C2 on modern EICR.
3. Single-RCD split-load board. 1990s–2015. RCD on some socket circuits, MCBs on all. Category C3 in most cases today, C2 if RCD coverage is incomplete.
4. 17th-Edition dual-RCD split-load board. 2008–2022. Two RCDs, MCBs on all circuits, split-load configuration. Compliant when installed; may be C3 today if plastic-enclosed in a habitable space.
5. 18th-Edition Amendment 2 all-RCBO board. 2022 onwards. Metal enclosure, RCBO per circuit, Type 2 SPD fitted, AFDD optional. Current standard.

When the swap becomes mandatory

BS 7671 does not require retroactive replacement of any board. A board that was compliant when installed remains legal. But three things push the swap:

1. EICR outcome. An Unsatisfactory EICR requires remediation of C1 and C2 findings to bring the report to Satisfactory. Where the board is the reason for the finding, replacement is the remedial route.
2. Private-rented mandate. The Electrical Safety Standards Regulations 2020 require an in-date Satisfactory EICR on every let property. If the board is causing the report to be Unsatisfactory, the landlord must replace it within 28 days.
3. Insurance and buyer requirements. Home insurance renewals sometimes ask about the board; conveyancers on a sale sometimes flag an old board as a defect on the electrical schedule. Neither has legal force, but both create commercial pressure to upgrade.

What a compliant 2026 board looks like

A consumer unit installed today, to be fully compliant with BS 7671:2018 Amendment 2:2022, has:

• Metal enclosure (required inside a habitable space since 2015)
• Type 2 SPD fitted as standard, unless risk-assessed out under Section 443
• Main switch or isolator to interrupt the supply for maintenance
• RCBOs on every circuit (preferred) or a split-load dual-RCD configuration (economy, still compliant)
• AFDD optional on domestic; recommended on socket circuits in higher-risk premises
• Correctly-sized main earthing conductor from meter to CU (16mm² is the current default on most domestic supplies)
• Main protective bonds to incoming metallic services (gas, water where metal-piped)

Half a day of on-site work once the DNO has cut the tails. Full test and inspection on completion. Electrical Installation Certificate issued. Building Regulations compliance certificate self-certified under Part P and posted within a fortnight.

Sources: BS 7671:2018 Amendment 2:2022; historical 17th Edition Amendment 3 (2015); IET On-Site Guide, 18th Edition.