EV Charging Cost Calculator
Compare the running cost of an electric car against petrol or diesel, with home and public charging priced separately.
How to use this calculator
- 1Enter your annual mileage and the EV's efficiency in miles per kWh.
- 2Set your home and public charging rates, and how much you can realistically charge at home.
- 3Enter the petrol car's real-world MPG, and pick imperial or US gallons.
- 4Optionally add a purchase price difference to see how long the savings take to recover it.
How the calculation works
EV cost = (miles ÷ mi/kWh) × blended rate petrol cost = (miles ÷ mpg) × litres per gallon × price per litre blended rate = home% × home rate + public% × public rate- mi/kWh
- EV efficiency. Typically 3–4, falling in cold weather and at speed
- blended rate
- The average price per kWh once home and public charging are weighted
- litres per gallon
- 4.546 for an imperial gallon, 3.785 for a US gallon — a 20% difference that flips MPG comparisons
The imperial and US gallon differ by about 20%, so a "40 mpg" car means quite different things either side of the Atlantic. Picking the wrong one distorts the whole comparison.
Charging location dominates EV running cost. Home overnight rates can be a fifth of public rapid rates, so the same car can cost 2p or 20p a mile depending only on where it plugs in.
Efficiency figures are optimistic in the cold. Battery chemistry and cabin heating together can cut range by 20–30% in winter, and motorway speeds cost more again.
Charging losses of 10–15% mean the kWh you are billed for exceed the kWh reaching the battery. Real-world cost per mile is therefore slightly above the naive calculation.
Worked example
10,000 miles, mostly home charging
- 1.Energy needed: 10,000 ÷ 3.5 = 2,857 kWh a year.
- 2.80% at the £0.08 overnight rate: 2,286 kWh = £182.86.
- 3.20% at the £0.79 rapid rate: 571 kWh = £451.43.
- 4.EV total £634.29, or £0.063 per mile.
- 5.Petrol at 40 mpg: 250 imperial gallons = 1,136 litres at £1.40 = £1,590.
- 6.The EV saves £956 a year — about 60% of the fuel bill.
Result: £956 a year saved
The same car with no driveway
- 1.Same 2,857 kWh, but all of it at the £0.79 public rate.
- 2.EV cost: £2,257 a year, or £0.226 per mile.
- 3.Petrol is unchanged at £1,590.
- 4.The EV now costs £666 a year MORE than petrol.
- 5.Identical car, identical mileage — the only difference is where it charges.
- 6.This is why "EVs are cheaper to run" is true for people with driveways and frequently false for those without.
Result: £666 a year worse than petrol
The driveway divide
The claim that electric cars are cheaper to run is true, false, or wildly true depending almost entirely on one thing: whether you can charge at home overnight.
A dedicated overnight EV tariff can be under 8p per kWh in the UK. Public rapid charging routinely exceeds 75p. That is a factor of nearly ten on the same electricity, into the same car. At 3.5 mi/kWh the identical vehicle costs about 2.3p a mile on the first and 22.6p on the second.
Petrol at 40 mpg and £1.40 a litre sits around 15.9p a mile — comfortably above home charging and comfortably below public rapid. So the same car genuinely saves a driveway owner most of their fuel bill while costing a flat-dweller more than the petrol car they replaced. Both experiences are real, which is why the public argument about EV running costs never resolves.
Why quoted efficiency is optimistic
Manufacturer efficiency figures, like manufacturer MPG, are measured under favourable conditions. Real-world consumption is worse, and two effects dominate.
Cold is the larger one. Battery chemistry is less efficient below about 10°C, and cabin heating draws directly from the traction battery rather than from waste engine heat. Together these can cut effective range 20–30% in winter. A car returning 4 mi/kWh in June may manage under 3 in January.
Speed is the other. Aerodynamic drag rises with the square of velocity, and EVs have no gearbox to hide it, so motorway cruising is markedly less efficient than urban driving — the reverse of a petrol car, which is at its worst in traffic.
Finally, charging is not lossless. Between 10% and 15% of the energy drawn from the wall never reaches the battery, and you are billed for all of it. Every real cost per mile is therefore a little above the naive calculation.
What this assumes, and where it stops
Assumptions
- Efficiency and MPG entered are real-world figures rather than official test values.
- Home and public rates are constant through the year.
- The petrol comparison uses the gallon type selected — imperial and US differ by about 20%.
- Charging losses are not added separately; enter a slightly lower efficiency to account for them.
Limitations
- Running costs only. Purchase price, depreciation, insurance, servicing, road tax and any congestion or emissions charges are not modelled, and they usually favour the EV.
- Assumes constant rates. Time-of-use tariffs, public network pricing tiers and subscription plans all complicate the real figure.
- Does not model efficiency loss in cold weather or at speed, which can be 20–30%.
- Charging losses of 10–15% are mentioned but not applied automatically.
- Not advice on which car to buy — total cost of ownership involves much more than fuel.
Common questions
Is an electric car cheaper to run than petrol?
It depends almost entirely on where you charge. Home overnight charging at 8p per kWh gives about 2.3p a mile against petrol's 16p, saving most of the fuel bill. Public rapid charging at 79p per kWh gives 22.6p a mile — more expensive than petrol. The same car, the same mileage, opposite conclusions.
How much does it cost to charge an EV at home?
A car doing 10,000 miles at 3.5 mi/kWh needs about 2,857 kWh a year. On a dedicated overnight tariff around 8p per kWh that is roughly £230 a year, against about £1,590 of petrol for the same distance at 40 mpg.
How many miles per kWh does an EV get?
Typically 3 to 4 in mixed driving. Efficiency falls substantially in cold weather, since battery chemistry is less efficient and cabin heating draws from the traction battery, and at motorway speeds where aerodynamic drag dominates. A car managing 4 mi/kWh in summer may return under 3 in winter.
How long does it take to recover an EV's higher purchase price?
Divide the price difference by the annual running-cost saving. A £5,000 premium against a £956 annual saving takes about 5.2 years on fuel alone — though that ignores servicing, road tax and depreciation, which usually shorten it. With mostly public charging the premium may never be recovered from running costs.
Sources
Formula and content last reviewed on .
Results are estimates for information only, not professional advice.
Related calculators
Tools people commonly use alongside the ev charging cost calculator.