EV vs petrol running cost
Electric cars are cheap to run on home charging and dear on public rapid chargers. This blends the two by your own charging mix, then shows the yearly saving against a petrol car.
Why the charging mix decides it
An electric car turns electricity into miles very efficiently, so on a cheap home tariff the cost per mile is tiny. The problem is public rapid charging, which can cost eight or ten times the home rate per unit. Blend enough public charging in and the per-mile cost climbs to meet petrol. This calculator asks for that split directly, because a headline EV saving that assumes home-only charging can be misleading for anyone who cannot plug in at home.
Worked example
At 9,000 miles a year, 3.5 miles per kWh and a 20% public share, the EV blends 8p home and 75p public electricity into about 6.1p a mile, or £550 a year. A 50 mpg petrol car at 140p a litre costs about 12.7p a mile, or £1,146 a year. The EV saves roughly £595. Push the public share up to about 55% and the two cars cost the same. On public chargers alone the EV would cost about 21.4p a mile, close to the petrol figure.
Common questions
Is an electric car really cheaper to run than petrol?
It depends almost entirely on where you charge. Charging at home on an off-peak tariff is far cheaper per mile than petrol. Relying on public rapid chargers can cost about the same as petrol, and sometimes more. This tool blends the two so the result reflects your own mix.
How is EV cost per mile worked out?
Take the car’s efficiency in miles per kWh, then divide your electricity price by it. At 3.5 miles per kWh and 8p per kWh at home, that is a little over 2p a mile. At a 75p public rapid charger it is over 20p a mile, which is close to the cost of petrol.
What electricity price should I use?
A dedicated EV off-peak tariff is often around 7p to 9p per kWh overnight. Public rapid chargers are commonly 60p to 80p per kWh. The blend slider lets you set what share of your miles come from each, because that share drives the whole result.
What if I cannot charge at home?
Then the savings shrink or disappear. On public-only charging an EV can cost as much per mile as a petrol car, so the case for switching rests more on emissions and the driving experience than on fuel cost. Set the slider to your real charging mix and the result will reflect it.
Does this include tax, insurance or depreciation?
No. This compares fuel and electricity only, the running cost that changes most between the two. Road tax, insurance, servicing and depreciation are separate, and electric cars now pay road tax too.