Consumer Unit Upgrade Guide 2026: Signs, Process & Regs

Your consumer unit, the board most people call the fuse box, is the heart of the electrics in your home. It takes the incoming supply and distributes it to every circuit in the property, with a protective device on each. If the board is old or lacks modern protection, everything downstream is running without a safety net. This guide covers how to tell if yours needs replacing, what a modern board includes under BS 7671:2018+A4:2026, and what happens on the day.

What a consumer unit actually does

Your consumer unit is the single point where the supply from the meter is split into the final circuits that feed the lighting, sockets, cooker, shower, boiler and outbuildings. Every circuit passes through a protective device that disconnects the circuit automatically if something goes wrong. The history of those protective devices tells you a lot about what you have:

• Rewireable fuses (the great-grandparent). A piece of fuse wire that melts when too much current flows. Protects the wiring from overheating. Does not protect you from electric shock.
• MCBs, miniature circuit breakers (the grandparent). Rocker switches that trip automatically and reset with a flick. Still only overcurrent protection.
• RCDs, residual current devices (the parent). Detect tiny imbalances in current caused by leakage to earth, and cut the power in under 30 milliseconds. This is what protects people from electric shock.
• RCBOs, combined protection (current standard). Overcurrent protection and residual current protection in one device per circuit. A fault only trips the affected circuit.
• AFDDs, arc fault detection (current amendment). Detect the signature of arcing faults, a leading cause of electrical fires. Required on specific circuits under BS 7671:2018+A4:2026 in HMOs, student accommodation and care homes.

For more on the difference, see fuse box vs consumer unit and MCB vs RCD vs RCBO vs AFDD.

Signs your fuse box needs replacing

• Wooden backboard. Pre-1990s installation with exposed timber behind the board.
• Rewireable fuse carriers. Round or rectangular pull-out holders with fuse wire inside, rather than rocker switches.
• No RCD protection. Modern boards have a switch labelled RCD or RCCB, or an RCBO on every circuit. If yours has none of these, the socket and lighting circuits have no shock protection.
• Split-load board with one side unprotected. Looks modern but only half the circuits pass through the RCD. Almost always a C2 on an EICR.
• Frequent tripping. Whole-house trips or a single circuit that trips repeatedly, especially from multiple circuits at once, often points at cumulative leakage on a shared RCD.
• Burn marks or discolouration. Scorch marks, warm spots, melted plastic around a terminal or device.
• Age. Any board older than 25 to 30 years is unlikely to meet current regulations.

What a modern consumer unit includes

• Steel enclosure. Non-combustible, mandatory for domestic installations since January 2016.
• 100 A main switch. Double-pole isolator at the origin of the final circuits.
• One RCBO per final circuit. Combined overcurrent and 30 mA residual current protection. A fault on one circuit only trips that circuit.
• Type 2 Surge Protection Device (SPD). Protects downstream equipment from voltage transients from lightning or grid events. A default expectation under BS 7671:2018+A4:2026 in most domestic premises.
• Arc Fault Detection Devices (AFDDs) on specified circuits. Required in HMOs, student accommodation and care homes under A4:2026. Recommended elsewhere.
• 25 mm tails and a 16 mm main earth. Current expectation for a 100 A single-phase supply.
• 10 mm main bonding. Green-and-yellow bonding clamped to gas and water service pipes within 600 mm of entry.
• Printed schedule of circuits. Fixed inside the cover, every circuit identified by function, device rating and reference method.

Old vs modern board, side by side

What BS 7671:2018+A4:2026 expects

The 4th amendment to the 18th Edition of the IET Wiring Regulations came into force on 15 April 2026 ^[1]. For a new or replacement consumer unit in a UK dwelling, the headline expectations are:

• 30 mA RCD protection on all socket outlets rated up to 32 A and all final circuits supplying lighting.
• Type A as the minimum RCD type for new circuits.
• Type B RCD or 6 mA DC sensing built into any EV charging circuit.
• Type 2 Surge Protection Device at the origin in most domestic premises.
• AFDDs on socket circuits in HMOs, purpose-built student accommodation and care homes.
• Non-combustible (steel) enclosure.
• Main bonding to gas and water service pipes at 10 mm minimum.

A compliant replacement therefore means more than just swapping the box: tails, earthing, bonding and the RCD/RCBO/AFDD specification all have to be right for the property type.

Why the existing wiring condition matters

A new consumer unit has to work safely with the circuits feeding out of it. Older installations often have legacy quirks that a shared RCD forgave but an RCBO does not. Two common ones:

• Borrowed neutrals. Two circuits sharing a neutral wire. A modern RCBO sees the shared neutral as a fault and trips the moment the circuit is energised. The fix is to separate the neutrals, which can mean opening up walls or running a new cable.
• High insulation resistance loss. Older rubber or early PVC insulation degrades and leaks small currents to earth. An RCBO with 30 mA residual sensitivity trips on circuits that used to run fine.

An EICR before the upgrade catches both. I can carry out the EICR and the replacement on the same visit, or split the two if remedial work is likely.

What happens on the day

1. Pre-visit surveyI look at the existing board, tails, main earth and main bonding, count circuits, check rooms each one feeds, and confirm access.
2. Supply isolationOn the day the supply is isolated at the meter or at the DNO cutout. The house is without power for the middle of the day, usually four to six hours.
3. Remove the old boardThe existing consumer unit is disconnected, labelled and removed. Undersized or damaged tails are replaced. Missing main bonding is installed.
4. Fit and wire the new boardThe new steel enclosure is mounted, the main switch, RCBOs and SPD are clipped into the busbar, and each circuit is landed, labelled and torqued to the manufacturer’s spec.
5. Test and certifyInsulation resistance, earth fault loop impedance, polarity, RCD trip times and continuity are measured on every circuit. Results go on an Electrical Installation Certificate.
6. Re-energise and hand overSupply back on, lights and sockets checked through with you, printed schedule fixed inside the cover, notifiable work registered with Building Control via NICEIC.

A fuller day-by-day walkthrough: Consumer Unit Upgrade, What to Expect on the Day.

Future-proofing for EV, heat pump, solar

Upgrading the board is a good moment to think about what you might connect to it in the next few years. Three things are worth mentioning during the survey:

• EV charger. A dedicated 7 kW charger circuit needs a Type B RCD or a charger with 6 mA DC sensing. Better to lay out the board for it now than retrofit later.
• Heat pump. Draws significant sustained current and usually wants its own circuit. Leave a spare way and adequate main fuse headroom.
• Solar PV and battery. Needs Type B RCD protection on the generation side, and often an additional isolator near the inverter.

A note on cost

Every consumer unit replacement is scoped on a site visit. Cost depends on circuit count, enclosure type, tails and earthing condition, whether AFDDs or Type B RCDs are needed, whether any cabling needs making good, and access. I give you a clear written estimate before any work starts. Book a consumer unit survey.