Consumer unit replacement: what you need to know
When an old fuse box should be replaced, what a modern consumer unit does differently, and what to expect on the day.
Published 11 November 2026 · By Positive Contractors, NICEIC Approved Contractor and Gas Safe registered
What a consumer unit does
The consumer unit, often still called the fuse box, is where your electricity supply is split into circuits for sockets, lights, the cooker and so on. Each circuit has a protective device that switches it off if something goes wrong. A modern unit also has RCD protection, which cuts the power in a fraction of a second if current leaks to earth, for example through a person.
Signs you may need a new one
- It still has old rewireable fuses (with fuse wire) rather than circuit breakers
- There is no RCD protection, or only some circuits have it
- Scorch marks, a burning smell, buzzing or heat from the unit
- Breakers tripping often without an obvious cause
- You are adding circuits, such as an EV charger, extension or new kitchen
- An EICR has recommended it
Plastic or metal?
Since 2016 the Wiring Regulations have required new consumer units in homes to have a non-combustible enclosure, which in practice means metal. This followed a number of fires where plastic units helped flames spread. An existing plastic unit is not illegal and does not have to be replaced just because it is plastic, but any replacement will be metal.
What happens on the day
- The power is switched off for most of the job, so plan for a day without electricity
- The old unit is removed and the new one fitted, with the circuits connected to new protective devices
- Every existing circuit is tested before it is reconnected
- Earthing and bonding are checked, and upgraded if needed
- Any circuit with a dangerous fault is not reconnected until it is fixed, and you will be told what is needed
Certificates and Part P
Replacing a consumer unit is notifiable work under Part P of the Building Regulations in England and Wales. A registered electrician, such as an NICEIC Approved Contractor, can self-certify it: you receive an Electrical Installation Certificate, and the work is registered with building control so a compliance certificate follows. Keep both, as buyers' solicitors and insurers often ask for them.
What it costs
The price depends on the size of the property, how many circuits there are, and what testing reveals about the existing wiring. As a general guide, the IET puts typical domestic consumer unit replacements at roughly £500 to £2,000 including installation. We price each job individually after seeing photos or surveying, and the quote is always in writing.
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Common questions
Do I need a whole rewire to change the consumer unit?
Not usually. Existing circuits can be connected to a new unit as long as they pass testing. If a circuit has a dangerous fault, it needs fixing before it is reconnected.
Will a new consumer unit stop my lights tripping?
If the tripping is caused by a fault on a circuit, the new unit will still trip, because that is its job. Testing during the changeover usually finds the cause so it can be fixed.
Do I need a new consumer unit for an EV charger?
Sometimes. It depends on whether your current unit has space and suitable protection. We check this before quoting for a charger.
Can a landlord leave an old fuse box in place?
Only if the EICR finds the installation safe. Old units with no RCD protection often lead to coded observations, so many landlords replace them during remedial work.
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