EV charger installation

A car charges for hours at a steady, heavy load. A 7 kW charger draws about 32 amps for as long as the car wants it: close to what an electric shower draws, but all night instead of ten minutes. So a chargepoint gets a dedicated circuit of its own from the consumer unit, never a spur off the sockets.

That circuit needs 30 mA RCD protection of a type suited to a car charger, and the board it comes from needs a spare way to take it. If your consumer unit is an old one with no space or no RCD protection, it may need replacing first, and the quote will say so.

The survey can start with photos. Send these on WhatsApp:

• The consumer unit, with its door open so the switches and labels show. Leave the cover on.
• The meter and the cut-out beside it: the sealed box the supply cable comes into, which holds the main fuse. It belongs to the network operator, so photograph it and leave it alone.
• The drive, the wall where you would like the charger, and where the car usually parks.
• The route between them, if the board is at the other end of the house from the drive.

From those we can see whether the supply has room for a charger, roughly how the cable would run and what to check on the visit. Then you get a written quote.

Every house has a main fuse in the cut-out, commonly 60, 80 or 100 amps. A charger running flat out on top of the oven, the shower and the kettle can ask for more than that.

Load management stops that happening. A CT clamp, a small sensor that clips round the meter tail, measures what the house is drawing, and the charger turns its own rate down while the house is busy and back up when it is not. The car charges a little slower at teatime, and the total stays within the main fuse.

Many chargers have load management built in. The clamp goes on at the meter and is wired or paired to the charger.

On most UK supplies, the neutral and the earth share one conductor in the street, the PEN conductor, and the earth in your house is connected to it. If that conductor ever breaks, the earth in the house can rise to a dangerous voltage. Inside, bonding keeps everything you can touch at the same voltage. Outside, a car standing on the drive is a different matter, because you are standing on the ground.

So a chargepoint needs protection against a lost PEN conductor. In most chargers sold now it is built in: the charger watches the supply and disconnects the car if it sees the signs of a PEN fault. Where it is not, another arrangement is needed, such as an earth rod for the charger alone, and the quote sets out which applies.

Outside, the cable is normally steel wire armoured (SWA): a tough black cable with a layer of steel wires under its sheath. It leaves the house through a sleeved hole in the wall and is clipped along it. Where it has to cross the drive it goes in a duct underneath, with warning tape above, so it is protected and can be found later.

On a short run, the cable size is set by the current the charger draws. On a long one it is set by voltage drop: the longer the cable, the more voltage is lost along it, and a thicker cable loses less. A charger at the far end of a long drive, or on a garage across the garden, can need a noticeably bigger cable than one on the wall beside the meter. We measure the route and size the cable for it.

A tethered charger has its lead fixed on. You unhook it from the holster and plug it into the car, and the lead lives on the wall. An untethered charger has a socket, and you use the lead that came with the car or one you buy. It looks tidier on the wall and lets you choose the length of lead, but the lead comes out of the boot every time.

Either way, check the length against where the charge port is on your car and how you park. A lead that only just reaches is a nuisance every day.

• Close to where the car parks, on the side its charge port is on, so the lead does not trail across a path or a doorway.
• At a comfortable height, clear of car doors and the bins.
• Where its app can reach your Wi-Fi, or a mobile signal, if it is a smart charger.
• On a solid wall, or a post set in the ground for the purpose, rather than a fence panel.

When the best spot for the car is a long way from the board, the length of that route sets the cable size, so we look at the charger position and the route together.

A chargepoint installation has to be notified to the network operator, the company that owns the cables in the street. Depending on the supply, some need the operator’s agreement before the charger is connected. We deal with that as part of the job.

A new circuit is notifiable under Part P, so building control is notified too, and you receive a Building Regulations compliance certificate along with the Electrical Installation Certificate for the circuit, with its test results. Keep both with the house paperwork.