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Electric vehicle charging questions

Heads up: I know very little about electrics.

Later this year I want to get an electric vehicle, to be stored on my driveway at the side of the house, in front of the garage. I imagine the EV charger would be located there, on the side wall of the house.

When fitting fast chargers for electric vehicles (32amps), I'm assuming the specialist fitters need to connect to the main house CU, rather than auxiliary ones?

I'm checking because my external garage (back-side of house) has no power at all, and I soon very plan to get power added to it- lights and a few double sockets. From what I've gathered that requires a new smaller CU wired from my main house CU (front, opposite side of house).

What I'm trying to determine is how much power I'll need, whether I need to factor in a possible 32A charging port for the future planned EV (as its nearer), or, if they would just connect to the main CU instead for that then I need not worry about it.

Just checking off things before I push ahead getting the garage fitted. Can anyone enlighten?

4 Answers from MyBuilder Electricians

Best Answer

An Electric Vehicle charging point must be supplied from its own dedicated circuit and be protected by either a type A or type B residual current device (RCD) or residual current breaker with over-current (RCBO). Whether the dedicated circuit is supplied direct from the main consumer unit in the house, or from a new sub-board in the garage is a matter of preference, convenience, and, of course, cost considerations. What is paramount is that both must be capable of supplying the additional load.

It is therefore absolutely essential that a load demand assessment be made by a qualified electrician prior to an EV charging point being installed. If the charging point is to be supplied from the sub-board that you are considering having installed in the garage, a load demand assessment will again have to be made so to ensure that the correct size of cable to supply the board is selected. In certain instances, the main incoming supply to the property may have to be upgraded by the local DNO (Distribution Network Operator).

It is also paramount that the existing means of earthing including main protective bonding is assessed and upgraded if necessary. Extraneous metallic parts such as taps and water/gas pipes and class I light fittings may have to be shielded or even replaced. Should the charging point be installed externally, or might reasonably be expected to be used to charge a vehicle located outdoors, then a dedicated earth rod will then need to be driven into the ground and connected to the charging point. Alternatively, an EV voltage monitoring and protection unit may be used where installation of an earth rod would be difficult to achieve or hazardous.

As the design and installation of Electric Vehicle charging equipment requires specialist knowledge, I would therefore recommend that you contact an OLEV authorised installer for further advice and a quotation. Using an OLEV authorised installer means that you may be able to claim a voucher under the Electric Vehicle Homecharge Scheme that would entitle you to a discount of up to £350 on the overall installation costs. If you use an electrician who is not an OLEV authorised installer, you will have to meet all of the installation costs yourself.

Finally, the local DNO must be informed whenever an EV charging point has been installed.

Hope this helps.


Answered 3rd May 2020

Why don’t you run all this past the electrician who you choose to put the supply in to the garage, then he can factor this in, do a few calculations and put a supply in that is of adequate size and a sub board that is big enough for the future.


Answered 6th Jun 2019

Some good answers already, and you are asking the right questions at the right time. An academic point but it may not be necessary to install earth rods as previously suggested, that would depend upon your supply earthing arrangement and/or manufacturing instructions. Some EV installations are very straight forward, a half days work installing the charging unit on the other side of the wall to a consumer unit, so OLEV might be a bit over the top.


Answered 11th Jun 2019

No need to complicate the answer it’s very simple. An EV charge point requires its own supply from the distribution board. If there is no space on the distribution board you can install a small garage unit. From this you will have to have an isolation switch prior to he EV unit. Depending on where you install that will depend on t type of wiring you use eg steel wire armoured cable or twin and earth.


Answered 1st Jul 2019

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