What is a granny charger?

Glossary · EV charging

How a granny charger works

“Granny charger” is the informal name for a portable charging cable with a standard 3-pin plug on one end and the car’s connector on the other. Pod Point calls it an EVSE supply cable for a 3-pin plug socket.^{[3]Pod Point, Everything you need to know about charging an electric car at home} You plug it into an ordinary wall socket and the car charges from the mains.

It is slow. Pod Point lists a 3-pin socket at 2.3kW, which adds about 8 miles of range per hour. Home charging points at 3.6kW or 7.4kW give about 15 to 30 miles of range per hour.^{[3]Pod Point, Everything you need to know about charging an electric car at home} Our page on how long it takes to charge at home compares the times.

The bigger issue is safety. A standard 3-pin plug is not built for the steady, sustained load of EV charging, and Pod Point says that can cause overheating.^{[3]Pod Point, Everything you need to know about charging an electric car at home} That is why it describes this method as a last resort and recommends it only as an occasional back-up.^{[3]Pod Point, Everything you need to know about charging an electric car at home}

Speed and risks compared

The rates and ranges are from Pod Point’s connector guide, which assumes a 60kWh battery.^{[1]Pod Point, EV charging connector types and speeds} The same guide labels 3-pin charging as slow, not best practice and for emergency use only.^{[1]Pod Point, EV charging connector types and speeds}

Extension leads make it worse. Pod Point says extension cables are not typically made to handle the high, sustained current needed for EV charging, which can lead to overheating or fire. It also says that a 3-pin socket takes over 24 hours to charge a 60kWh battery, so the car is often left charging unattended overnight, which compounds the risk.^{[2]Pod Point, Can you charge an electric car with an extension cable?} Pod Point says experts and safety groups, including Electrical Safety First, advise against using extension cables to charge a car at home.^{[2]Pod Point, Can you charge an electric car with an extension cable?}

If a 3-pin charge is ever unavoidable, Pod Point’s advice is to watch the charge rather than leave it overnight, to stop if you see damage or overheating, and to follow the car maker’s guidance.^{[2]Pod Point, Can you charge an electric car with an extension cable?} It does not recommend making it a habit. Any work on the socket or the wiring behind it is for a registered electrician.

Example

Tom in Armley has an electric car and a garage with a 3-pin socket. He plugs the car in each night. The car does not finish charging by morning, so he leaves it plugged in over the weekend too. Pod Point’s figure for a 60kWh battery on a 3-pin socket is over 24 hours.^{[2]Pod Point, Can you charge an electric car with an extension cable?}

Tom asks about a dedicated charger. A dedicated home charger is a compact weatherproof unit on its own circuit.^{[3]Pod Point, Everything you need to know about charging an electric car at home} Our installation page explains that we run a new circuit from the charge point back to the consumer unit and test and certify it once it is live.^{[4]Martin Day Electricians, Home EV charger installation in Leeds} That removes the sustained load from the socket and brings the charging time down to a night.

What people get wrong

Many drivers think a granny charger is just a slower version of a proper charger. The difference is not only speed. A socket is not designed to run at a steady load for hours, whereas a dedicated charger is built for it and has built-in safety features.

The second mistake is relying on it because it works. Pod Point also says drivers choose a dedicated home charger for its built-in safety features.^{[3]Pod Point, Everything you need to know about charging an electric car at home} A 3-pin charge may seem fine for weeks. Pod Point still treats it as an emergency option, and our installation page notes that charging overnight from a 3-pin plug is slow and may not finish by morning.^{[4]Martin Day Electricians, Home EV charger installation in Leeds}

The bottom line

A granny charger is a 3-pin portable cable that charges an electric car at about 2.3kW. It is slow and puts a steady load on a socket that was not designed for it, so manufacturers treat it as an emergency back-up. For regular charging, a dedicated home charger on its own circuit, fitted by a registered electrician, is faster and safer.