Consumer Unit Upgrades Explained
A consumer unit change is more than swapping a box. You're taking responsibility for the circuits it feeds, so the assessment and paperwork matter as much as the board.
Replacing a consumer unit is one of the most common upgrade jobs, driven by old fuse boards, added circuits, or the need for RCD and surge protection. But when you change the board, you take on responsibility for the circuits connected to it, which is why the job starts with an assessment.
This guide covers what a consumer unit upgrade involves — assessing the existing installation, selecting the board, and the certification and notification required.
Key takeaways
- Assess the existing circuits before quoting — you're certifying what the new board feeds.
- Modern boards are non-combustible (metal) with RCBO protection and usually an SPD.
- Pre-existing defects found during the change must be recorded and addressed.
- A consumer unit change is notifiable under Part P and needs an EIC.
- Test every circuit as part of the change, not just the new board.
Assess before you quote
Because you become responsible for the circuits the new board feeds, inspect and test them first. Bonding, cable condition, and any borrowed neutrals or shared circuits all need to be understood before you commit to a price, because a straightforward board swap can uncover work that has to be done first.
This is where a change goes wrong most often — quoting a board swap, then finding the installation isn't ready for one.
Quote after the survey
A quick inspect-and-test up front stops the classic consumer unit change that balloons once the cover's off.
Choosing the board
Modern consumer units are non-combustible metal enclosures. An all-RCBO board is usually the best choice — it gives per-circuit 30 mA protection and isolates faults to a single circuit — and an SPD is fitted unless a risk assessment rules it out.
Consider AFDD requirements for the premises type, and leave spare ways for future circuits like an EV charger.
Doing the change
Isolate, prove dead, and transfer circuits methodically, checking and re-terminating conductors as you go. Confirm main protective bonding is present and correctly sized — an unconfirmed main bond is a frequent hold-up because bathroom supplementary bonding can't be omitted without it.
Address any defects you find, and record anything that needs follow-up.
Testing and certification
Test every circuit — continuity, insulation resistance, polarity, Zs, RCD operation — not just the new devices. The change is certified with an Electrical Installation Certificate covering the board and the full schedule of test results.
As notifiable work, it's notified through your competent person scheme or Building Control.
Whole board on one certificate
TradePlanr's EIC captures every circuit, device and test result for the change, ready to sign on site.
Frequently asked questions
How long does a consumer unit change take?
A straightforward domestic change is often a day, but that assumes the installation is ready. The inspect-and-test and any remedial work — bonding, defective circuits — can extend it, which is why the assessment comes first.
Do I have to test all the circuits?
Yes. When you change the board you certify the circuits it feeds, so every circuit is tested and recorded on the EIC, not just the new protective devices.
Is a consumer unit upgrade notifiable?
Yes. Replacing a consumer unit is notifiable work under Part P and requires an EIC plus scheme notification or Building Control involvement.
From guidance to action
Related guides
Consumer Unit Regulations (BS 7671)
The regulations behind consumer units — non-combustible enclosures, RCD/SPD/AFDD provision and RCBO boards.
SPDs: Surge Protection Devices
SPD types, the BS 7671 risk assessment, and how to install surge protection correctly.
Main Protective Bonding Explained
What main protective bonding does, conductor sizes, and where bonding is required to BS 7671.
