How to use an extension lead to charge your electric car

Can-I-charge-my-electric-car-with-an-extension-cord

If your granny cable doesn’t reach the socket, you can use a heavy-duty 13A extension lead to bridge the gap. You will get around 8 miles of range per hour.

You should not use extension leads rated lower than 13A because they are only designed to power low current appliances and gadgets. Never use a domestic multi-socket extension lead to charge an electric car.

Extension leads are considered a fire hazard by some manufacturers. The risk comes from overheating because most extension cords are not designed to be used for the duration it takes to charge an EV.

Additionally, only use 3-pin sockets you have confidence in. 3-pin sockets are not designed to deliver maximum current for hours at a time.

Most EV manufacturers don’t recommend extension cords because they have no control over the quality of third-party products. If in doubt, ask the manufacturer of the product for advice before using it.

You can also pick up extension leads for electric cars, such as this one from Tough Leads which extends a granny charger from 2m to 25m. 

Can I use an extension lead to charge my electric car?

Yes, you can charge your electric car with an extension lead, but we only recommend extension cords rated for 13A continuous (sold as heavy-duty).

Here’s what one looks like:

The extension lead needs to be waterproof and rated for outdoor use if it will be exposed outdoors.

The reason we recommend a 13A heavy-duty extension lead is that anything lower can overheat charging an electric car.

However, bear in mind that most extension leads are not designed to remain in use for the time it takes to charge an electric car. You should ask the extension lead manufacturer if you have any doubts about safety.

Plugging into a 2.3kW 3-pin socket will give you around 8 miles of range in 60 minutes, which might be enough to limp you to a public charger. It isn’t powerful enough to replenish an electric car battery overnight, unless you start at 90%.

Guidelines for using an extension lead to charge an electric car

Here are some guidelines when using an extension lead to charge your electric car:

  • Never use a domestic multi-socket extension lead.
  • Only use a 13A heavy-duty extension lead.
  • If the extension lead will be exposed outdoors, it needs to be waterproof.
  • Before using an extension lead, inspect it to make sure it’s in good condition and make sure the plug socket it’s plugged into is also in good condition.
  • If the extension lead is on a reel (such as a 13A outdoor extension cord) you need to fully unravel the cable so that it can dissipate heat properly.
  • Touch the wall socket, charger head and extension lead now and again to get a feel for the temperature. If things gets too hot to hold the back of your hand against them, pull the plug.

What does your EV manufacturer say?

Check with your manufacturer and follow their advice first and foremost.

Some EV manufacturers, such as BMW, recommend that you don’t use an extension cord to charge your electric car. They cite fire hazards as the reason. Other manufacturers sell adapters.

Never daisy chain extension leads

Daisy-chaining extension leads is extremely dangerous because it increases heat and risks spikes in the power supply. You risk overloading the cable which will trip the circuit breaker and could cause a fire.

The bottom line is if you need emergency power and have access to a 13A extension lead, using it for an hour or so should be fine – but keep an eye on it for heat. Avoid extension cords you are unsure about for safety reasons.

Can I charge overnight with an extension cord?

Yes, you can charge overnight but use a 13A extension lead, fully uncoiled. You will add around 60-miles of range from 8-hours of charging.

For faster-charging speeds, get an electrician to install a Commando socket or a smart charger. 16A Commando sockets charge at speeds of 3.6kW (15 miles of range per hour) while 32A chargers go up to 7.4kW (30 miles of range per hour.

Best smart chargers to consider

3-pin sockets and Commando sockets get the job done, but smart chargers are better because they let you schedule charge times and integrate your EV tariff for kWh price caps.

Check out our EV charger reviews for ideas, or start with these:

  • Easee One: The Easee One is an excellent charger (read our full Easee One review). It offers 7.4kW charge speeds, RFID, cable locking (to turn the untethered charger into a tethered charger) and a good app with smart scheduling.
  • Wallbox Pulsar Plus: Another solid choice is the Wallbox Pulsar Plus (read our full Wallbox Pulsar Plus review). It’s the smallest smart charger we’ve tested and a great option if you want something inconspicuous.

Overall

Charging an electric car with an extension lead is perfectly safe so long as you use the right extension lead. You can use a granny charger extension lead designed for the job, or a 13A heavy-duty extension lead rated for outdoor use.

Never use a domestic multi-socket extension lead, and if you have any doubts about the safety of an extension lead or socket, don’t use them.

Alfred Maxwell
Alfred drives a Tesla Model 3 Standard Range Plus but has his eye on a fully-electric pick-up truck. He'd love an electric Ford Ranger, which should be a real thing in a few years!