How to choose the right consumer unit when upgrading your fuse board

Helpful video reference. John Ward (jwflame), a qualified electrician based in Dorset, gives a practical overview of modern consumer unit technology in his talk "John Ward Talks About New Consumer Units — Types of RCDs, Types of SPDs and AFDD (Fuse Boxes)". John runs Flameport Electrical and has been explaining UK electrical standards on YouTube for over a decade. The video covers the key differences between device types clearly and is worth watching before you start getting quotes for a board change.

1. Understand why old boards need replacing

There are three types of older board you are likely to come across in a UK home.

Rewireable fuse boxes offer no RCD protection at all. When a fuse blows, some householders replace it with wire of the wrong rating, which defeats the protection entirely. These boards are genuinely dangerous and any electrician inspecting one will recommend replacement.

Old plastic consumer units were the standard for many years but became a concern after several fires were traced to arcing inside units. Amendment 1 (2016) to BS 7671 required all new consumer units to be metal-clad to contain any internal fire. A plastic board is not automatically unsafe, but it cannot be legally installed new today.

Single-RCD boards were common in the 1990s. The one RCD covers everything. If it trips due to a fault, the whole house loses power. That is not a safety issue in itself, but it causes real inconvenience and makes fault-finding harder. The choice of new board matters precisely because it determines how your home responds to a fault.

2. Understand the three main current board types

(a) Dual-RCD split-load board. Two RCDs cover two groups of circuits. The board is cheaper to supply and to fit than an all-RCBO unit, and it still meets all the requirements of BS 7671 Amendment 2. The downside is that a single RCD trip takes out every circuit on that side of the board. If your shower and kitchen ring are both on the same RCD and the shower develops a fault, you lose the kitchen sockets too. This type is still sold and installed, but is increasingly considered the budget option.

(b) All-RCBO board (high integrity). Each circuit has its own RCBO, which combines an MCB and a 30 mA RCD in a single device. A fault on any one circuit isolates only that circuit. Everything else stays on. The parts cost more and there is more labour in wiring individual devices, so the overall job price is higher. This is Richard's standard recommendation for replacement boards.

(c) Boards with AFDDs. Arc fault detection devices monitor for the kind of electrical arcing that precedes many house fires. BS 7671 Amendment 2 recommends AFDDs on socket circuits in sleeping accommodation, which in practice means rented properties with bedrooms. The cost premium over a standard RCBO is significant. For owner-occupied homes the recommendation is weaker, but some homeowners choose to fit them on bedroom circuits for peace of mind.

3. Understand the SPD requirement

BS 7671 Amendment 3 (2024) made surge protection effectively mandatory in new and replacement consumer unit installations in most UK domestic properties. The assessment process in the standard almost always points to a Type 2 SPD being required.

A Type 2 SPD is fitted at the board by your electrician. It adds around £80 to £120 to the job. What it does is clamp transient overvoltages before they reach your appliances. These surges can come from lightning strikes on nearby infrastructure or from switching operations on the local grid, and they can silently degrade electronics over time or cause immediate damage.

If you have a heat pump, a battery storage inverter or solar panels, an SPD is especially worthwhile, as these systems contain sensitive control electronics. If your area has a history of power cuts or visible voltage fluctuation, that is another reason to make sure it is specified.

When comparing quotes, check whether the SPD is included. Some lower quotes omit it. Ask directly.

4. Decide how many ways you need

A "way" is one circuit position in the board. Before your electrician visits, it is worth listing every circuit in your current board: lighting upstairs, lighting downstairs, ring main A, ring main B, cooker, immersion heater, shower, outdoor socket, garage, and so on. Count them up.

Then think about the next ten years. Do you plan to add an EV charger? A garden room? A second shower? Each of those will need its own way. Fitting a board that is already full means a second board later, which costs considerably more than going slightly larger now.

A 14-way board gives a typical three-bedroom semi comfortable headroom. An 18-way suits larger houses or homes with several outbuildings and dedicated circuits. The cost difference between a 14-way and an 18-way is relatively small at the point of installation.

5. Factor in the rewire question

A new consumer unit does not fix old wiring. If your installation dates from before 1990, there is a reasonable chance the wiring is reaching the end of its useful life. Pre-1990 PVC-insulated cables can become brittle and cracked, particularly in roof spaces where temperatures swing significantly.

If an EICR has identified C1 or C2 codes on the wiring itself (not just on the board), those need addressing. Fitting a new board on top of condemned wiring gives you a modern, certificated board but leaves the underlying problems in place. Richard will always carry out a visual inspection of the accessible installation before quoting for a board change, so that any remedial work can be included in the quote rather than appearing as a surprise later.

6. Get three things in writing at completion

When the job is done, your electrician should hand you three documents. If any of these are missing, ask for them before paying the final balance.

• Minor Electrical Installation Works Certificate or Electrical Installation Certificate. This is your copy of the electrical certification for the work. Keep it with your house documents.
• Building Regulations Compliance Certificate. This confirms that the Part P notification has been filed with the local authority. It is the document that proves the work was done by a competent person and registered correctly. You will need it if you sell the property.
• Completed circuit schedule. A label on the inside of the board door listing every circuit by name. If yours is currently blank or illegible, a new board is the opportunity to set that right.

When to call us

Richard replaces consumer units across Sandwich, Deal, Dover and east Kent, typically in a single day. The standard specification is a metal-clad all-RCBO board with SPD, EICR and Part P certificate included. Prices from around £600 fitted for a straightforward domestic installation.