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The short version
- Consumer unit replacement in London costs from £400, typically £400–£700 including VAT.
- Old wiring, not the board, is what usually changes the price.
- A new RCD board trips on faults an old fuse box ignored, so test the circuits first.
- Replacing a consumer unit is notifiable in England: expect an EIC and a Building Regulations certificate.
Replacing a consumer unit in London costs from £400, typically £400–£700 including VAT, for a straight swap in a typical home. The price covers the new board, testing every circuit and the certificates. What moves it is rarely the board itself: it is whether the existing wiring passes the tests a modern RCD board depends on.
| Job | Guide price (VAT included) |
|---|---|
| Consumer unit replacement | from £400 (typically £400–£700) |
| EICR before the work, 1-bed flat | from £120 |
| Tracing a fault on an existing circuit | from £100 |
| Partial rewire, where a circuit cannot be saved | from £2,000 |
These are guide prices, not fixed quotes. The figure for your home is confirmed once the installation has been tested, for the reason explained below.
The price covers the board, the testing and the certificates
A consumer unit replacement is more than unscrewing one box and fitting another. A guide price should include:
- A new consumer unit in a non-combustible metal enclosure
- 30 mA RCD protection for the socket and lighting circuits that require it
- Surge protection, where the regulations call for it
- Testing every circuit, with the results recorded
- An Electrical Installation Certificate, and notification to building control
Moving the board to a new position or adding new circuits is extra work, and is quoted separately.
Old wiring moves the price, not the board
Why an old fuse box hides faults
An old fuse box with rewireable fuses protects against overload, but it has no RCD. A small fault can sit in the wiring for years without anyone noticing, because nothing on that board is built to detect it.
What a new board does differently
A new board's 30 mA RCDs trip on current leaking to earth. A damaged cable, a neutral shared between two circuits or damp in a fitting, all ignored by the old fuses, will trip the new board the day it goes in.
Electrical industry guidance is plain about what happens next. A faulty circuit is repaired, or it stays disconnected until it is. It is not connected to the new board as it stands.
Testing comes before the replacement
Because the wiring decides the job, the installation should be tested before a replacement is booked. That means an EICR, or at the least a survey including insulation resistance tests on every circuit. Contractor guidance says the work should not go ahead without one.
If you already have a recent EICR, read it first. Any C2 or FI observations, or notes about low insulation readings, show what a new board is likely to expose. Our guide to what an EICR report tells you explains the codes.
An EICR in London costs from £120 for a 1-bed flat, including VAT. When you ask anyone for a consumer unit price, ask whether they will test first.
Three possible outcomes after testing
| What testing finds | What happens | Guide price (VAT included) |
|---|---|---|
| The circuits test well | The board is replaced like for like | from £400, typically £400–£700 |
| One or two circuits have faults | The faults are traced and repaired, then the board goes in | the board, plus fault finding from £100 |
| A circuit cannot be saved | That circuit is rewired, or stays disconnected until it is | partial rewire from £2,000 |
Whatever testing finds, any extra work is quoted in writing before it starts, so the figure never changes halfway through the job.
Nothing forces an upgrade, but a new board must meet today's rules
Homeowners and landlords
No law makes a homeowner replace a working fuse box. The rules apply when work is done: new work must meet BS 7671, the UK wiring regulations, and must not leave the installation less safe than before.
Landlords are in a different position. An EICR may record missing RCD protection as an observation, and anything coded C1, C2 or FI has to be put right within 28 days.
What a new domestic board must have
- A non-combustible enclosure, in practice steel, required in homes since January 2016
- 30 mA RCD protection for socket circuits rated up to 32 A and for lighting circuits
- Surge protection in most homes, unless what it protects does not justify the cost
The two certificates you should receive
Replacing a consumer unit is notifiable work under Part P of the Building Regulations in England. That means two documents, issued at two different points:
- An Electrical Installation Certificate (EIC) when the work is finished, confirming the new board and its circuits were tested to BS 7671.
- A Building Regulations compliance certificate within 30 days, after the installer's registration scheme has notified building control.
Keep both. A buyer's solicitor, a letting agent or an insurer may ask for them. Work by an installer who is not registered with a scheme has to be notified to building control separately, before it starts.
For a price on your own board, call 07727 619854 or see our electricians in London. We are NICEIC approved, so the certificate and the building control notification are part of the job.
Frequently asked questions
Often, yes, if the existing circuits pass testing. Faults the old board tolerated will trip the new RCDs, so they are repaired first, or the affected circuit stays disconnected until it is rewired.
No law requires a homeowner to replace a working fuse box. It is worth considering, because a board with rewireable fuses gives no RCD protection against electric shock. Landlords should act on whatever their EICR records.
An Electrical Installation Certificate when the work is finished, and a Building Regulations compliance certificate within 30 days. Replacing a consumer unit is notifiable work in England, so a registered installer notifies building control for you.