What Affects the Cost of a Consumer Unit Upgrade?

Replacing an old fuse box with a modern consumer unit is one of the most worthwhile electrical upgrades in an older home. It adds RCD protection, which can cut the power in a fraction of a second if someone touches a live part, and it makes faults much easier to find. But people are often surprised that quotes vary. That's because the box itself is only part of the job. Here's what actually decides the cost. For what the work involves on the day, see our consumer unit upgrades page.

The size of the installation

A small flat might have six circuits. A large house with an extension, a garage, an electric shower, an outdoor supply and an EV charger might have twenty or more, sometimes split over more than one board. Every circuit has to be connected, tested and recorded, so the number of circuits is a far better guide to the time involved than the number of bedrooms. Larger installations may also need a bigger enclosure or a second board.

RCBO or RCD layout

There are two common ways to arrange protection in a new board. In a dual-RCD board, circuits are split into two groups, each protected by one RCD. If one circuit has a fault, every circuit in that group goes off. In an RCBO board, every circuit has its own combined breaker and RCD, so a fault only affects that one circuit.

Both approaches meet the wiring regulations when designed properly. RCBO boards cost more because each device does more, but they're far less disruptive when something trips, and they make nuisance tripping much easier to diagnose. Some layouts mix the two. We'll explain which suits your home and give you the choice.

The condition of the earthing and bonding

Before a new board can be fitted, the main earthing conductor and the protective bonding to the water and gas pipes have to meet current standards. In many older homes they don't: the earth cable may be undersized, the bonding may be missing or disconnected, or the earthing arrangement from the supplier may need checking. Bringing these up to standard is a necessary part of the job, not an optional extra, and how much needs doing varies from house to house.

Faults found during testing

This is the factor nobody can predict. Old fuses often don't notice small leakage problems, but an RCD will. Before the new board is energised, every circuit is tested. If that reveals damaged insulation, a borrowed neutral, a crossed connection or water in an outside light, it has to be found and put right before the circuit can go on the new board. Sometimes that's a quick fix; sometimes it's a sign that part of the house needs rewiring. Our guide to full versus partial rewires explains when that point is reached.

A good quote will explain how faults will be handled. Our approach is to stop, show you what we've found, and price any extra work before carrying it out.

Access and position

Where the old board is matters. A board on an accessible wall in a utility room is straightforward. One squeezed into an under-stairs cupboard full of meters, or mounted high in a hallway, takes longer. Moving the board to a new location means extending the tails and every circuit, which adds work. Some locations also need a fire-resistant enclosure or a different position to suit current guidance.

Other things that can affect the price

• Whether the supplier's main fuse or meter tails need attention, which may involve the network operator.
• Surge protection, which is now recommended in most installations.
• Extra circuits you'd like added at the same time, such as for an EV charger.
• Making good around the new board and any decorating afterwards.

Comparing quotes

When you compare prices, ask each electrician whether they've allowed for earthing and bonding upgrades, whether the board is RCBO or dual-RCD, whether surge protection is included, and how they'll handle faults found during testing. Ask too which certificates you'll receive. With those answers, quotes become much easier to compare like for like.

For a fixed quote, call 01235 430442.