Electrician
Replacing a fuse box with a modern consumer unit
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The fuse box, or consumer unit, is where your electricity supply is divided into circuits and where the protective devices sit that switch off a circuit when something goes wrong. Replacing an old one is among the most common electrical jobs, and among the most misunderstood: the new unit is only as good as the circuits connected to it. This page explains when a replacement is worthwhile, what the job involves and why testing comes first. The request is bought by exactly one electrician covering your area.
- Exactly one business. Your request is handed out once. After that, no other business sees it.
- You know who will be in touch. Before the business receives your contact details, we send you its name, address and phone number.
- Withdraw at any time. You can withdraw your consent at any time – using the link in our email.
When a replacement makes sense
An old unit is not automatically dangerous. Electrical Safety First notes that older consumer units without residual current devices or circuit breakers are not necessarily unsafe and do not always need upgrading; an inspection tells you. Rewireable fuses with fuse wire, a wooden back board, scorch marks, a unit with no spare ways for a circuit you need, or an inspection report that records the lack of residual current protection as a defect are the usual reasons to replace.
Other triggers are new loads that need their own circuit, such as an EV charger, a heat pump or an electric shower, and a rewire, which normally includes a new unit. If you are planning one of those jobs, do the consumer unit at the same time rather than twice.
What a modern unit contains
A modern consumer unit has a main switch, circuit breakers for each circuit and residual current protection that cuts the power within a fraction of a second if current leaks to earth, for example through a person. That protection can be shared across a group of circuits by a residual current device, or provided circuit by circuit with RCBOs. RCBOs cost more but mean that a fault on one circuit does not also switch off the others on the same group.
Depending on the installation, the electrician may also fit surge protection and, on some circuits, arc fault detection. The quote should explain what is fitted and why; a unit designed for your circuits is better than the largest box on the shelf.
Make a requestWhy testing comes first
Old fuses tolerate faults that modern protection will not. A circuit with a small leak to earth, or a neutral connected to the wrong circuit, may have worked for years and will trip a new residual current device immediately. That is not a fault of the new unit; it is the new unit doing its job.
A good electrician therefore tests the existing circuits before quoting or at the start of the job and explains what has to be put right. The new unit cannot be certified until the circuits connected to it are safe. Ask how faults found on the day will be priced, so the final bill does not come as a surprise.
The parts that are not yours
Your meter and the sealed service head or cut-out with the main fuse belong to the supplier and the network operator. The electrician works on your side of the meter. If the cut-out is damaged, the main fuse is too small for the new loads, or a separate isolator switch is needed to work safely, the network operator or your supplier may have to be involved, and that can add days to the timetable. A photo of the whole meter position helps the electrician see this in advance.
Replacing a consumer unit is notifiable work in England and Wales. A registered electrician self-certifies it and you receive an Electrical Installation Certificate with test results for every circuit and, from the scheme, a Building Regulations compliance certificate.
Checklist for the quote
- make and model of the unit, number of ways and space for future circuits
- type of residual current protection: shared RCDs or RCBOs
- surge protection or arc fault detection, if proposed, and the reason
- testing of existing circuits and how remedial work is priced
- earthing and main bonding upgrades to gas and water pipes
- how long the power will be off
- certificates and notification
From your request to the electrician
Describe the current fuse box, ideally with a photo, confirm your mobile number and email, and your request is offered to electricians nearby without your personal details. One firm can buy it; once bought, it disappears from the list. The electrician pays Offrano, not you.
We email you the firm's name, address and phone number before it sees your details. Nobody is obliged to buy, and a request without a buyer is withdrawn after 21 days. Offrano confirms that buyers are registered businesses but does not judge their work, so check the electrician's registration with a competent person scheme.
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Frequently asked questions
Is my old fuse box dangerous?
Not necessarily. Many older units still work safely, even without residual current devices. An Electrical Installation Condition Report shows whether yours has defects that need action. Scorch marks, a burning smell or a hot unit need an electrician straight away.
Why does my new consumer unit keep tripping?
Usually because it is detecting faults on existing circuits that the old fuses ignored, such as damaged cable, a faulty appliance or a borrowed neutral. The electrician tests each circuit to find the cause.
RCD or RCBO: which is better?
Both give residual current protection. RCBOs protect each circuit individually, so a fault only turns off that circuit. A split-load unit with shared RCDs costs less, but a fault can switch off several circuits at once.
Can any electrician replace a consumer unit?
It is notifiable work, so the electrician should be registered with a competent person scheme to self-certify it. Otherwise Building Control must be notified before the work starts.
Will my power supply need upgrading too?
Only if the main fuse or the network operator's cut-out is too small or in poor condition, often when adding a heat pump or EV charger. The network operator deals with its equipment; the electrician can advise whether to ask.
Ready to make your request?
Describe your project – your request goes to exactly one business.
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