Many EVs come with an emergency cable in the boot that plugs into an ordinary household socket. For a few hours in an unusual situation, that is handy. As a regular way of charging it is a poor idea, mostly because of heat.
How much do you actually get?
A normal wall socket usually delivers about 2.3 kW (230 V at 10 A). Some cars charge even lower by default, because the emergency cable limits the current. Here are a few examples, assuming a consumption of 16 kWh per 100 km:
- 8 hours of charging gives 8 x 2.3 = 18.4 kWh. That is roughly 115 km of range.
- Filling an empty 60 kWh battery takes 60 / 2.3 = about 26 hours.
- If the car is set to 1.84 kW (8 A), the same 60 kWh takes well over 32 hours.
If you drive 30 km a day, one night on a wall socket is enough. If you drive 100 km or more every day, you will never catch up.
Why is it risky?
Think of a kettle. It draws about the same current, but it switches off after a few minutes. A car asks for that current for hours. Everything along the path warms up: the socket, the plug, the wiring in the wall and the fuse. Sockets in an older installation often have loose contacts or corrosion as well. That raises the resistance, and with it the heat.
A plug that feels lukewarm after an hour is normal. A plug that gets properly warm or hot is not. If that happens, stop straight away.
When can it work?
- As an emergency solution, for example on a visit or on holiday, when there is no free charger nearby.
- On a socket in a recent installation, on its own circuit and not shared with other appliances.
- If you can lower the charging current in the car. Many cars have this setting in the menu. Check the manual for a “reduced current” or “charging current” option. Charging at 8 A produces less heat than at 10 A.
What should you avoid?
- An extension lead or multi-socket strip. Many are not made for hours at 10 A, especially when coiled on a reel.
- A socket that already feels warm, discoloured or loose.
- Charging somewhere damp without a protected socket. An outdoor socket has to be suitable for it.
- Sharing the circuit with other big loads. If a tumble dryer or iron is on the same circuit, it fills up faster.
- Charging while nobody is home or while you sleep, before you know how the socket copes. Test it during the day the first time and check the plug with the back of your hand after an hour.
What to do if something warns you
If the fuse or the residual-current device trips while charging, do not simply try again. Unplug, let everything cool down and look for melting or black marks on the plug, the socket or the cable. If you see any, stop using that socket and have it checked. If the car itself reports a charging fault or overheating, follow the manual and find another place to charge, for example on the charger map.
When does this not apply?
If you have a dedicated charging socket that an electrician put on its own circuit for this purpose, that is a different situation. It is no longer an ordinary wall socket. Ask your installer what power that circuit can handle.
Have your installation checked
If you still want to charge from a socket regularly, first have an electrician check the circuit: cable thickness, fuse, residual-current protection and the condition of the socket itself. Without that check you do not know how old or how loaded that circuit is.
Better: a wallbox
If you charge at home every week, a wallbox is the safe choice. It sits on a separate circuit, is built for hours of charging and can be faster. Read home charging for what it costs and what you need, and how to choose a wallbox for the differences between models. No driveway at home? Then EV charging without a driveway is a better place to start.