What is a 'way' in a consumer unit?

A 'way' refers to a single slot available for a circuit breaker (MCB or RCBO). For example, a 10-way consumer unit has space for 10 individual circuits.

Should I choose a Dual RCD or RCBO board?

RCBO boards are modern standard. If one circuit fails, only that circuit loses power. In a Dual RCD board, a single fault can knock out half the circuits in your house. RCBOs are safer and more convenient but slightly more expensive.

Is surge protection (SPD) mandatory?

Under current UK 18th Edition (Amendment 2) regulations, surge protection is effectively mandatory for almost all domestic installations to protect against lightning strikes and power surges.

How many spare ways should I leave?

We recommend leaving at least 2 to 4 spare ways. This allows for future additions like an EV charger, solar panels, or a garden office without needing to replace the entire board.

What is a 'way' in a consumer unit?

A 'way' refers to a single slot available for a circuit breaker (MCB or RCBO). For example, a 10-way consumer unit has space for 10 individual circuits.

Should I choose a Dual RCD or RCBO board?

RCBO boards are modern standard. If one circuit fails, only that circuit loses power. In a Dual RCD board, a single fault can knock out half the circuits in your house. RCBOs are safer and more convenient but slightly more expensive.

Is surge protection (SPD) mandatory?

Under current UK 18th Edition (Amendment 2) regulations, surge protection is effectively mandatory for almost all domestic installations to protect against lightning strikes and power surges.

How many spare ways should I leave?

We recommend leaving at least 2 to 4 spare ways. This allows for future additions like an EV charger, solar panels, or a garden office without needing to replace the entire board.

Consumer Unit Sizing

Plan your electrical distribution board with spare capacity for the future.

Lighting Circuits

Socket Circuits (Ring)

Cooker / Oven

Electric Shower

EV Charger

External / Garage

Future Spares

Suggested Setup

Recommended Board Size

10-12 Way

Based on 9 active & spare ways

Circuit Type

RCBO

Highly Recommended

Safety Standard

18th Ed.

A3 Amendment

SPD Required

Under the 18th Edition Amendment 2, **Surge Protection Devices (SPD)** are now required in almost all UK installations to protect sensitive electronics from voltage spikes.

Important: Electrical work in the UK must be carried out or certified by a **Part P registered** electrician. This calculator is for planning purposes only and does not replace professional design.

The UK Guide to Consumer Units

Planning Your Install

Choosing a new consumer unit (often called a fuse box) is one of the most critical decisions in any home renovation. It is the heart of your home's safety system, protecting you from electric shocks and fire risks.

Most modern UK homes require between 8 and 14 circuits. However, with the rise of **Electric Vehicles (EV)** and **Air Source Heat Pumps**, the demand for board space is increasing rapidly.

Standard Circuit List

Lighting Upstairs & Downstairs
Ring Main Upstairs & Downstairs
Kitchen Sockets
Cooker / Oven Circuit
Smoke Alarms / Boiler

RCBO vs Dual RCD

In the past, **Dual RCD** boards were popular because they were cheaper. However, they are prone to 'nuisance tripping'—where a fault in your toaster could turn off your fridge and your lights at the same time.

**RCBO (Residual Current Breaker with Overcurrent)** technology is now the gold standard. Every circuit has its own individual protection. This is safer, more reliable, and is the choice of most professional electricians in 2026.

Never Fill Every Slot

A common mistake is buying a consumer unit that is *just* big enough. If you have 10 circuits, do not buy a 10-way board. Buy a **14-way or 16-way** board. The extra cost is negligible compared to the cost of a future board upgrade when you decide to install solar panels or an EV charger.

Consumer Unit & Electrical FAQ

Legal Warning

Changing a consumer unit is **not a DIY job**. It is a major electrical installation that falls under **Part P of the Building Regulations**. It requires specialized testing equipment and a Building Control certificate or an Electrical Installation Certificate (EIC) from a registered professional.