EV Charger and Electric Shower: Is Your Main Fuse Big Enough?

An electric shower, an electric oven and now an EV charger can each draw a large current, and in many London homes they all share one supply with a single main fuse. Before adding a charger, it is worth knowing whether your supply can cope. This guide explains the main fuse, how load is worked out, and the options if capacity is tight.

What the main fuse is

The main fuse, sometimes called the service fuse or cut-out, sits in a sealed box near your meter and belongs to the network operator. Most UK homes have a 60, 80 or 100 amp main fuse, and the rating is often printed on the fuse carrier. Do not open or tamper with it. If you cannot see the rating, an electrician can check.

How much the big loads draw

• A 9.5 kW electric shower draws around 40 amps while it runs.
• A typical 7 kW EV charger draws around 32 amps for hours at a time.
• An electric oven and hob together can draw a large current when everything is on.

Electricians do not simply add these numbers together, because not everything runs at once. Instead they carry out a maximum demand assessment that allows for normal use. On a 60 amp fuse with an electric shower, there may be little room left for a charger running at full power.

The options if capacity is tight

• Load management: many smart chargers can measure the whole house and slow down when the shower or oven is on, then speed up again. This is often the simplest answer.
• A main fuse upgrade: the network operator can sometimes upgrade a 60 amp fuse, which may be free or low cost, depending on the supply.
• Charging at night: scheduling the charger for night hours avoids clashes with showers and cooking.

Check the consumer unit too

Even with enough supply capacity, the consumer unit needs space and suitable protection for a new circuit. Our guide to electric shower upgrades covers the shower side, and our EV blog explains when you need a new consumer unit for a charger.

Book a survey

Energy North Ltd checks supplies and installs chargers across North, East and West London with City & Guilds certified electricians. See our EV charger installation page.