Consumer Unit & Fuse Box Upgrades: BS 7671 A4:2026 and Part P Explained

• Old rewirable fuses (fuse wire in ceramic holders) or a wooden backboard.
• No RCD protection, or only partial RCD protection.
• Frequent tripping, scorch marks, buzzing or a burning smell — stop using it and call an electrician.
• You're adding an EV charger, heat pump, solar PV or home battery.

An old board isn't automatically unsafe, but an inspection (EICR) will tell you whether it needs upgrading.

Since the 18th Edition, consumer units in domestic premises must be housed in a non-combustible enclosure — in practice a metal consumer unit — or in a non-combustible cabinet. This reduces the risk of a fault inside the board spreading fire into the home.

A dual RCD board splits circuits across two RCDs. It's cheaper, but one fault can switch off half the house.

An RCBO board gives every circuit its own combined breaker and RCD, so a fault on one circuit only switches off that circuit. It costs more but avoids nuisance tripping and makes fault finding easier. The right RCD type (A, F or B) should be chosen to suit the appliances on each circuit.

A surge protection device (SPD) is typically fitted in a new domestic consumer unit to protect electronics from transient overvoltages. Arc fault detection devices (AFDDs) are recommended for socket circuits and required in some higher-risk premises — ask your electrician whether they suit your home.

Amendment 4:2026 adds a dedicated chapter for stationary batteries and stresses that protective devices must be suitable for two-way energy flow where solar, home batteries or vehicle-to-home systems feed the installation. If you're planning any of these, mention it before a board change so the new consumer unit and protective devices are chosen with that in mind.

A consumer unit change isn't just swapping a box. The electrician must confirm the earthing arrangement and check main protective bonding to incoming gas and water pipes. If bonding is missing or undersized, it will need correcting as part of the work.

Replacing a consumer unit is notifiable work under Part P in England. After the work, every circuit is tested and you should receive:

• An Electrical Installation Certificate (EIC) with a schedule of test results.
• A building regulations compliance certificate (via a registered competent person scheme) or confirmation from building control.

Keep these safe — you'll need them when selling or remortgaging.

A typical domestic board change takes most of a day, with power off for much of it. Faults found on existing circuits during testing may need fixing before they can be reconnected — a good electrician will explain these before going further.

Want the bigger picture? Read our BS 7671 18th Edition guide.