Consumer unit
Plain English. Practical detail. UK context.
A consumer unit distributes electricity to circuits in a home and houses protective devices. It is often called a fuse box, although modern units generally use circuit breakers and other devices rather than rewireable fuses.
Safety: use a registered electrician, for example one registered with a competent person scheme such as NICEIC or NAPIT, for electrical installation work. Do not remove covers or open electrical equipment yourself.
Last reviewed: (editorial review against the public sources listed below).
What it means in practice
A replacement needs assessment of the existing installation as well as selection of a new enclosure and compatible devices. Earthing, bonding, circuit condition, space and the proposed protective arrangement affect the job. Do not promise that swapping the box will cure an unexplained circuit fault.
Agree what inspection, testing, remedial work and certification the scope includes. A label showing circuit names should reflect the actual installation, not an old schedule copied without checking.
For homeowners
Ask the electrician what is being replaced, why, and whether the quotation allows for defects discovered during testing. Keep the area accessible and discuss the likely loss of power while work takes place. The main switch should not be treated as permission to open the unit: parts associated with the supply can remain dangerous even when downstream circuits are switched off.
Practical checks
Keep the circuit schedule and installation paperwork after the work. If a device repeatedly trips, report the symptom rather than repeatedly resetting it without investigating the cause.
What the different devices do
A main switch, an MCB, an RCCB, an RCBO, surge protection and arc-fault detection are not interchangeable names. An MCB addresses overcurrent; an RCCB provides residual-current protection without its own overcurrent function; an RCBO combines those functions. The right combination depends on the circuits and installation. Ask the electrician to identify the protection proposed and how a fault might affect other circuits. A bigger enclosure does not increase the network supply's capacity. Nor does a fashionable device layout establish that retained wiring is sound. Where future equipment is planned, such as a heat pump or chargepoint, include it in the design brief rather than assume a spare slot guarantees a simple later addition.
The relevant standard and completion records
The IET identifies BS 7671:2018+A4:2026 as current following the October 2026 transition. Some product guides still refer to earlier amendments; the designer must apply the appropriate current requirements and assembly compatibility instructions. For an England dwelling, Approved Document P explains notification and electrical safety; other UK nations have their own framework. Obtain the installation certificate, relevant schedules and any separate building control evidence for a replacement. An EICR of existing wiring is a different document. The handover should show normal user controls, labels and test functions without asking the homeowner to remove covers or handle internal equipment.
Frequently asked questions
Does a new consumer unit mean the house has been rewired?
No. Replacing the consumer unit does not replace the cables and accessories throughout the home. Ask what was tested and what existing wiring was retained.
Can breakers from different manufacturers be mixed?
Physical fit is not evidence of compatibility. The electrician must follow the consumer unit assembly manufacturer’s instructions and the relevant installation requirements.
Sources and further reading
Public sources and further reading. Sources checked: 8 November 2026. Consult the original for details and later changes.