Your consumer unit (fuse box) may need upgrading if it still has rewirable fuses, has no RCD protection, shows scorch marks or a burning smell, trips often without an obvious cause, or has no space for a new circuit such as an EV charger or electric shower. Age alone is not a reason to replace one. An inspection shows whether the existing board is safe to keep or whether an upgrade is worthwhile.
What a consumer unit does
The consumer unit takes the supply from the meter and splits it into separate circuits for sockets, lighting, the cooker, the shower and so on. Each circuit is protected by a fuse or a circuit breaker (MCB), which cuts the power if the circuit is overloaded or short circuits.
Modern units also have RCDs, which detect current leaking to earth and switch off very quickly. That is what reduces the risk of a serious electric shock from a damaged cable or a faulty appliance. An RCBO combines a circuit breaker and an RCD for a single circuit.
Signs it may need upgrading
- Rewirable fuses: fuse wire held in ceramic or plastic carriers
- No RCD protection, or RCDs covering only some circuits
- Scorch marks, melted plastic, a burning smell, crackling or buzzing
- The unit or its cables feel warm to the touch
- Frequent tripping that cannot be traced to one appliance
- Cracked covers, missing blanks or any exposed live parts
- No spare space for a circuit you are planning to add
Scorching, burning smells, heat and buzzing are not things to wait on. Switch off at the main switch if it is safe to do so, and get it looked at. Our guide on why a fuse or breaker keeps tripping explains when to stop resetting and get help.
Rewirable fuses, missing RCDs and older enclosures
Rewirable fuses still work, but they react more slowly than circuit breakers and can be re-wired with the wrong size of wire. A board with no RCDs gives no extra protection against electric shock, and current regulations call for RCD protection on most socket circuits and in bathrooms, among other places.
For some years the wiring regulations have also required new consumer units in homes to have a non-combustible enclosure, usually metal. An older plastic unit is not unsafe for that reason alone and does not have to be replaced because of it, but it is one factor in the decision, particularly if it sits under the stairs.
Adding new circuits
An EV charger, an electric shower, a kitchen extension or a garden room each usually needs its own circuit. An old board may have no space, or may not provide the protection the new circuit requires, and that is often the point at which an upgrade makes sense. If you are planning a charger, see what to check before an EV charger is fitted, and for new circuits in general our wiring installations page.
What an upgrade involves
The existing circuits are tested first. Old fuses do not notice small leaks to earth, so a faulty appliance, a damp outside light or a damaged cable can go unnoticed for years. New RCDs will react to those faults, which is why they need to be found before or during the changeover.
For a typical home the power is off for most of a working day. Earthing and bonding are checked and brought up to standard where needed, and every circuit is labelled. If you want to know where your board stands before deciding, an electrical inspection will tell you.
Certificates and regulations
Replacing a consumer unit is notifiable building work under Part P of the Building Regulations in England. It must be notified to building control, either through a registered competent person scheme or directly to the council's building control.
You should receive an Electrical Installation Certificate with the test results, and a building regulations compliance certificate once the work has been notified. Keep both, as buyers' solicitors often ask for them. For advice on an older board, see our fuse replacement and consumer unit page or send details through the quote form.
Common questions
Do I have to replace an old fuse box?
No. There is no rule that a consumer unit must be replaced because of its age. If an inspection shows it is in good condition and protects the circuits properly, it can stay, and recommended improvements are your choice.
How long does a consumer unit replacement take?
For a typical home the power is usually off for most of a working day. It can take longer if testing finds faults on existing circuits or if the earthing and bonding need work.
Why do new RCDs sometimes trip after an upgrade?
Old fuses do not detect small leaks to earth, so faults can sit unnoticed for years. Once RCDs are fitted they react to those faults, which is why the existing circuits are tested first.
What paperwork should I get?
An Electrical Installation Certificate with test results, and confirmation that the work has been notified to building control. Keep both for when you sell or let the property.
Can I replace a consumer unit myself?
It is not a DIY job. It involves working next to the incoming supply, testing every circuit with specialist equipment and notifying building control, so it needs a competent electrician.