The consumer unit, commonly called the fuse board or fuse box, is the central distribution point for a property's electrical installation. It houses the main switch, miniature circuit breakers (MCBs) and residual current devices (RCDs) that protect individual circuits and interrupt supply automatically when a fault is detected.
Some older consumer units use rewirable or cartridge fuses and have limited RCD protection. Their age or fuse type alone does not establish that the installation is unsafe; an electrician assesses its condition and the protection needed.
A consumer unit replacement is a notifiable category of work under Part P of the Building Regulations in England. A registered competent person can self-certify and notify the work through their scheme.
Alternatively, the appropriate building control route must be arranged for the work. An Electrical Installation Certificate should be issued on completion.
The work involves isolating the incoming mains supply, safely disconnecting and removing the old unit, installing the new consumer unit, reconnecting all circuits, carrying out a full programme of electrical tests, and restoring the supply. Before the replacement begins, the electrician will carry out a check of the existing wiring to identify any issues that should be addressed at the same time.
Adding RCD protection across all circuits, upgrading to a split-load board, or making space for additional circuits to serve a new extension or appliance can all be incorporated at this stage. During the work, the property will be without electrical supply while the unit is changed over.
The duration depends on the number of circuits and the condition of the existing wiring. Planning for this in advance, for example by catering for any equipment that cannot be without power, is worth considering before the appointment.