EV Charging Cost Calculator

Start by entering your battery size in kilowatt hours (kWh). This is the usable capacity of your car, which you can find in the vehicle handbook or the manufacturer specification.

Set your current charge and target charge as percentages. The calculator works out the energy added between those two points. The target must be higher than the current charge, otherwise there is nothing to add and the calculator shows a warning instead of a misleading number.

Enter your electricity rate in pence per kWh. This is how UK tariffs are quoted. The 28p default is illustrative, so replace it with your own home, off-peak, or public charger rate for an accurate figure.

Adjust the charging efficiency if you know it, or leave it at the 90% default. Finally, set your real-world miles per kWh to see the cost per mile. Every result updates live as you type, with no submit button to press.

The calculator first finds the energy added to the battery. That is the battery size multiplied by the difference between the target and current charge percentages. A 60 kWh battery taken from 20% to 80% adds 60 times 60% which is 36 kWh.

Next it finds the energy drawn from the grid. Because charging is not perfectly efficient, the energy you pay for is higher than the energy that reaches the battery. The calculator divides the energy added by the charging efficiency. At 90% efficiency, 36 kWh added means about 40 kWh drawn from the grid.

The cost for this charge is the energy drawn multiplied by the rate in pounds. The rate is entered in pence, so it is divided by 100 first. At 28p per kWh, 40 kWh costs 40 times 0.28 which is 11.20 pounds, not 1,120.

Cost per mile reflects the grid energy you pay for: the rate divided by your charging efficiency, then by your miles per kWh, so (0.28 / 0.9) / 3.5 is about 9 pence per mile. The full charge cost applies the same method to a complete 0 to 100% charge, including charging losses.

The headline figure is the cost for this charge in pounds, based on the charge window and rate you entered. Use it to compare a quick top-up at home against the same energy from a public charger.

Cost per mile turns your electricity rate into a running cost you can compare directly with petrol or diesel. It depends on your real-world efficiency, which falls in cold weather and at motorway speeds, so check it against your own trip data.

Full charge cost shows the price of a complete 0 to 100% charge at your rate, a useful reference even if you rarely charge to full. Energy added shows the kWh that reach the battery alongside the slightly higher figure drawn from the grid, which is what you actually pay for.

These figures are estimates for planning and comparison. Real costs vary with battery condition, temperature, charger type, and how your tariff prices peak and off-peak periods. They are not financial advice.