The short answer
A straightforward consumer unit replacement usually takes around 4–8 hours — often a single working day — with the power off for most of that time. The electrician isolates the supply, removes the old board, fits and wires the new consumer unit, then carries out the testing needed to issue the Electrical Installation Certificate. The job can run into a second day if testing finds faults in the existing wiring, which is common in older properties, because those have to be put right before the installation can be certified. So a sound installation is usually a day; one that throws up problems on inspection can take longer.
Most homeowners want to know how long they'll be without power. For a standard job it's a single day; the main thing that extends it is faults found when the new board is tested. Here's how the day usually runs.
Typical timings
- Straightforward job~4–8 hours
- Power offfor most of the day
- Usual spanoften one working day
- If faults foundmay extend to a second day
- Ends withtesting + EIC
What happens on the day
- Isolation: the electrician safely isolates the incoming supply, so the power is off for most of the work.
- Removal & install: the old board is removed and the new consumer unit is fitted and wired to the existing circuits.
- Testing: each circuit is tested to confirm it meets the wiring regulations.
- Certification: the results are recorded and the Electrical Installation Certificate is issued, with the Part P notification made.
What can make it take longer
The usual reason a job runs past a day is faults found during testing. When the new board is fitted, every circuit is tested properly — sometimes for the first time in years — and an older installation can reveal problems such as poor connections or damaged cable that were hidden before. Those have to be corrected before the installation can be certified, which can mean a second visit. It isn't padding; certification depends on the circuits passing, so the honest timescale allows for what an inspection might uncover.
Want a clear timescale for your home?
We'll match you with a vetted, registered electrician who assesses your installation, gives you a realistic timescale, and explains how any faults found on testing would be handled.
Frequently asked questions
How long does it take to replace a consumer unit?
A straightforward replacement usually takes around 4–8 hours — often a single working day — with the power off for most of that time. It includes removing the old board, fitting and wiring the new one, and testing for the certificate.
Will my power be off all day?
For most of the day, yes. The supply is isolated while the old board is removed and the new consumer unit is fitted and wired, then restored once testing is complete. Your electrician can tell you the likely off period for your home.
Why might the job take more than a day?
If testing finds faults in the existing wiring — common in older homes — they have to be put right before the installation can be certified, which can push the work into a second visit.
Sources & further reading
- Total Skills — consumer unit replacement cost and process
- Electrical Safety First — replacing a consumer unit (best practice guide)
Figures on this page are typical UK ranges drawn from published sources and depend on your specific property and installation. They are guidance, not a quotation.