How much does it cost to charge an EV with Octopus?

Charging an electric car at home costs far less than filling a petrol tank, and the maths behind it is simple: the number of kilowatt-hours you put into the battery multiplied by the unit rate you pay for each one. On Octopus, the cheapest route for most EV drivers is the Intelligent Octopus Go tariff, which moves your car's charging into a cheap overnight window it schedules for you. Use the calculator on this page to put real numbers to your own car, mileage and the current rate.

Charging an electric car at home costs far less than filling a petrol tank, and the maths behind it is simple: the number of kilowatt-hours you put into the battery multiplied by the unit rate you pay for each one. On Octopus, the cheapest route for most EV drivers is the Intelligent Octopus Go tariff, which moves your car's charging into a cheap overnight window it schedules for you. Use the calculator on this page to put real numbers to your own car, mileage and the current rate.

The simple sum behind every home charge

Charging an electric car comes down to one piece of arithmetic: the number of kilowatt-hours (kWh) of electricity you put into the battery, multiplied by the unit rate you pay for each kWh. There are two easy ways to find the kWh figure. For a full charge it is roughly your car's usable battery size, and most EVs sit somewhere between about 40 kWh for a small city car and 75 to 100 kWh for a large SUV. More usefully, for everyday driving you only replace the miles you actually drove, so the sum becomes miles driven divided by your car's efficiency in miles per kWh, with real-world figures typically around 3 to 4 miles per kWh. Multiply whichever kWh number you land on by your overnight unit rate and you have the cost of that charge. The calculator on this page does exactly this, so you can drop in your own battery size, mileage and the current rate rather than work it out on paper.

Why charging overnight on Intelligent Octopus Go costs less

The unit rate in that sum is where Octopus's EV tariff, Intelligent Octopus Go, earns its keep. Instead of charging the same price around the clock, the tariff gives you a guaranteed cheap off-peak window every night, currently 11:30pm to 5:30am, when electricity is far cheaper than the daytime rate. You tell the Octopus app how much charge you want and by when, and it automatically schedules your car to fill up inside that window, often grabbing extra cheap half-hours outside it too when wholesale prices dip. Crucially, that low overnight rate covers your whole home during the window, not just the car, so a dishwasher, washing machine, hot-water tank or home battery run overnight all benefit. Because the per-kWh price you slot into the sum is the cheap overnight one rather than a flat day rate, the cost of a home charge drops sharply, which is why charging at home overnight works out far cheaper per mile than petrol or public rapid charging. We deliberately aren't quoting a pence figure here, because the rate varies by region and moves with the market; check the live number on octopus.energy and feed it into the calculator.

Putting real numbers to your own driving

A worked example shows how small the daily figure usually is. Say you drive 30 miles on an average day and your car manages around 3.5 miles per kWh: you have used roughly 8.5 kWh, so a typical day's driving needs only about 8 to 9 kWh back into the battery overnight. Multiply that by the off-peak rate and the nightly cost is genuinely modest, and because most people top up the miles they drove rather than charging from empty to full every night, you rarely pay for a whole battery at once. Scale that up across a week or a year and you get a realistic running cost to set against what you would otherwise have spent on fuel. The calculator on this page is built to do this with your numbers: enter your battery size or daily mileage, your car's efficiency and the current overnight rate, and it returns a cost per charge, per mile and over a year. That is far more reliable than any single headline figure, because it reflects how you actually drive.

The honest caveats the simple sum leaves out

A back-of-envelope sum gets you close, but a few real-world details nudge the true cost up. Home charging isn't perfectly efficient, as roughly a tenth of the electricity is lost as heat during AC charging, so your meter records a little more than lands in the battery. There is also a daily standing charge you pay regardless of how much you charge, just as on any tariff. The cheap rate only applies inside the overnight window, so topping up during the day or in a hurry costs significantly more, and public rapid chargers can cost several times the home overnight rate, which erodes the savings if you can't charge at home. Intelligent Octopus Go also needs a working smart meter and either a compatible EV or a compatible smart charger such as an Ohme, Andersen or Octopus unit, so it suits homes with off-street parking far better than flats without a charge point. If most of your charging happens away from home or during the day, the headline savings shrink, so be honest with yourself about how and where you charge before banking them.

How to get on the EV tariff, and £50 to start

There is an order of play worth knowing. Smart tariffs like Intelligent Octopus Go are only available once you are an Octopus customer with a working smart meter, so the route in is to join Octopus first and then move onto the EV tariff free of charge whenever your car or charger is ready. The smart way to join is through a referral link, because doing so adds £50 of credit to your account, paid as bill credit rather than cash, and added automatically once your switch fully completes and your first monthly Direct Debit clears, usually around four weeks and sometimes longer if your old supplier is slow. It costs you nothing extra. Use the referral link on this page to start your switch: sign-up happens entirely on Octopus's own website, your supply is never interrupted because it is the same pipes, wires and meter, and the move is protected by the Energy Switch Guarantee. One thing to get right is that the £50 only attaches if you arrive through the referral link directly; sign up via a price-comparison site and Octopus pays that site instead of you. Octopus is the UK's largest electricity supplier, used by around one in four homes, runs on 100% renewable electricity and is a long-standing Which? Recommended Provider, so you would be joining a mainstream, well-rated supplier and picking up £50 on the way in, before you even switch onto the tariff that makes EV charging so cheap.

FAQs

Switch to the UK’s most awarded energy supplier! Switch to Octopus Energy and you’ll get £50 credit once your switch is complete. T&Cs apply (only one switching offer per household).