Consumer Units
A consumer unit — commonly called a fuse box — is the central hub of your home's electrical system. It's where the incoming electricity supply from the grid is divided up into individual circuits (lighting, sockets, cooker, immersion heater, etc.) and protected against faults and overloads.
The large isolator switch that cuts all power to the house simultaneously. In an emergency or when working on the electrics, this is what you turn off.
Each circuit has its own MCB — a switch that automatically trips if the circuit is overloaded or short-circuited. MCBs replaced rewirable fuses in modern boards and reset by simply switching back on.
RCDs protect against electric shock by detecting tiny imbalances in current flow (which occur when electricity is flowing through a person). They trip within 40 milliseconds — fast enough to prevent a fatal shock in most cases.
An RCBO combines the functions of an MCB and RCD in a single device. In a modern consumer unit, each circuit gets its own RCBO — so a fault on one circuit trips only that circuit, not a whole section of the house. This is the current gold standard.
Found in older properties. Contains ceramic fuse holders with wire that "blows" when a circuit is overloaded. Does not provide RCD protection. Should be replaced.
Standard from the 1990s to mid-2010s. Has MCBs for each circuit, protected by two RCDs. When one RCD trips, it takes out half the house. Better than rewirable fuses but not current best practice.
Current best practice. Every circuit has its own RCBO. A fault on one circuit trips only that circuit. Provides full overload, short-circuit, and RCD protection per circuit.
AFTA Electrical covers Essex, Suffolk, Norfolk, Cambridgeshire, and Hertfordshire. NAPIT & TrustMark registered.
They're the same thing — "consumer unit" is the technical term used since the 1990s, while "fuse box" is the older colloquial name. Modern consumer units contain MCBs or RCBOs rather than actual fuses.
Key signs: it contains rewirable fuses, it's a plastic-cased older board, it trips frequently, your EICR has raised codes against it, or you need to add new circuits and there are no spare ways.
An RCBO provides both overload/short-circuit protection (like an MCB) and RCD shock protection — individually per circuit. If one circuit faults, only that circuit trips rather than half the house.
Most domestic consumer unit replacements cost £595–£795 fully installed, including the new board, circuit testing, EIC, and NAPIT Part P building regulations notification.
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