Granny Chargers: When Charging an EV From a Three-Pin Plug Is OK

Most electric cars come with, or can use, a portable charging cable that plugs into an ordinary three-pin socket. It is often called a granny charger. It can be handy, but it is not designed to be the main way of charging every day. This post explains when a three-pin plug is fine, when it is not, and what to check first.

How a granny charger works

A granny cable has a control box in the middle and plugs into a standard household socket. It charges much more slowly than a wall charger, so a full charge can take a very long time on a larger battery. It also draws a high current from the socket for many hours, which is much harder on the socket and wiring than a kettle or vacuum cleaner. See our guide on how long it takes to charge at home.

When a three-pin plug can be OK

• Occasional top-ups, for example when visiting family or staying away.
• A plug-in hybrid with a small battery, if the socket and wiring are in good condition. See our post on plug-in hybrids at home.
• A short stop-gap while you wait for a wall charger to be installed.

When it is not a good idea

• Through an extension lead or cable reel. Most car makers warn against this, and it is a common cause of overheating.
• From an old socket, a socket that feels warm, or one with scorch marks or a loose plug fit.
• From a socket in a garage or outbuilding with no RCD protection.
• With the cable trailing across a pavement or shared path.
• As the only way of charging a large battery car every day.

Check the socket first

If you plan to use a granny cable regularly, ask an electrician to check the socket and the circuit it is on. A dedicated outdoor socket on its own RCD-protected circuit is much safer than an indoor socket with a cable through a window. Our main blog explains safe outdoor sockets.

Why most drivers end up with a wall charger

A wall charger is faster, designed for long charging sessions, includes the protection the regulations require, and usually supports smart scheduling on cheaper overnight tariffs. For most London drivers with off-street parking, it is the safer long-term choice. See our post on getting a charger before or after buying the car.

Energy North Ltd installs home chargers and outdoor sockets across North, East and West London with City & Guilds certified electricians. See our EV charger installation page to book a survey.