Older Fuse Box
Older-style fuse boxes may lack features found in modern consumer units.
Plain English
What Is a Consumer Unit?
The consumer unit is the box, usually near your meter, where the electricity supply coming into your home is divided into the separate circuits that feed your sockets, lights, cooker, shower and so on. Most people still call it the fuse box, and older versions genuinely did contain rewireable fuses.
Inside a modern unit you will find a main switch that isolates the whole installation, plus a protective device for each circuit. Those devices are designed to disconnect their circuit automatically under certain fault conditions — for example an overload, a short circuit, or current escaping to earth.
What Does It Do?
It does three jobs. It gives you a single point to switch the electricity off. It splits the installation into circuits so a problem in one place does not take out the whole house. And it holds the protective devices that disconnect a circuit when something goes wrong, which is the part that matters most for safety.
Why Consumer Units Are Sometimes Upgraded
Consumer units are usually changed because the existing board no longer suits the installation it serves. That might be an older board with rewireable fuses, a board with no residual current protection, a unit that is physically full with no way to add circuits for a kitchen or an extension, or one showing signs of damage or overheating. Whether an upgrade is appropriate for your home is something an electrician should confirm after inspecting and testing the installation.
Modern Circuit Protection
MCBs (miniature circuit breakers) protect a circuit against overload and short circuit, and reset with a switch rather than needing fuse wire.
RCD protection monitors for current escaping to earth — the sort of fault that can occur when a cable is damaged or someone contacts a live part — and disconnects the supply quickly when it detects it.
RCBOs combine both functions in a single device per circuit. Their practical advantage is that a fault on one circuit disconnects only that circuit, rather than taking out half the house.
Surge protection (SPDs) can be fitted to help protect connected equipment against transient overvoltages, for example from switching events or nearby lightning activity. Whether it is appropriate depends on the property and the installation, and your electrician will assess this as part of the design.
Which devices are appropriate for your installation is a design decision based on the circuits present, their condition and the current edition of the UK wiring regulations at the time the work is carried out. We will explain what we are proposing and why before any work begins.
The Testing Involved
Testing is not an optional extra on a consumer unit change — it is central to the job. The existing circuits are inspected and tested before the new board goes on, so that any faults are found while they can still be discussed and priced. After the new unit is fitted, the installation is tested again to confirm everything performs correctly, and you receive the appropriate certification.
What Happens During a Consumer Unit Replacement
- 1We inspect and test the existing installation and discuss anything we find with you.
- 2The supply is isolated safely and the power goes off for the working part of the day.
- 3The old board is removed and the new consumer unit is mounted and wired in.
- 4Each circuit is reconnected, identified and clearly labelled.
- 5The installation is tested, the supply is restored and the results are recorded.
- 6We walk you through the new unit and how to use it, and issue your certification.
Why the Installation Should Be Assessed First
A new consumer unit protects the wiring behind it — it does not repair it. If a circuit has a pre-existing fault, fitting sensitive modern protection can simply reveal it, sometimes as repeated tripping the moment the new board is energised. That is why we test first: so problems are identified, explained and priced up front, rather than becoming an unwelcome surprise after the work.
Questions Worth Asking
- Will the existing installation be inspected and tested before the board is changed?
- What will happen if testing finds a fault on one of the circuits?
- What protection will the new consumer unit provide, and why?
- How long will the power be off, and when will that be?
- Will the new board be labelled so I know what each circuit does?
- What certification will I receive when the work is finished?
- Is any making-good needed around the board, and is it included?
- Is the price fixed, and what could change it?
Common reasons
Reasons Homeowners Ask About an Upgrade
Not sure whether your board needs attention? Call 07833 918205 and describe it to us.
Regular Tripping
If circuits regularly trip, the cause should be professionally investigated.
Home Renovation
Electrical upgrades or renovations may require changes to the existing installation.
Additional Electrical Demand
Modern households often use significantly more electrical equipment than properties originally had.
Electrical Safety
A qualified electrician can inspect the installation and advise whether improvements are appropriate.