EV vs Petrol and Diesel Running Cost Calculator
Compare the energy cost of two vehicles over the same annual mileage. Use petrol or diesel economy in UK mpg, US mpg or litres per 100 km, or EV battery use with an allowance for charging losses.
How to use EV vs Petrol and Diesel Running Cost Calculator
1. Choose the currency used for results. 2. Choose the correct economy measure for each vehicle. Match the fuel price to litres or kWh, and use the same annual distance for both. 3. Change a value to update the results, or select Calculate. Review the chart and notes with the total. 4. Use Copy results, Share results or Download result graphic to keep the answer. Shared links include your figures. 5. Reset restores the editable example inputs.
Why use this tool?
A car’s energy cost depends on both consumption and the price you pay. A low electricity rate at home can give a different comparison from a public charging rate, just as two fuel prices can change a petrol-versus-diesel calculation. This tool keeps energy costs separate from ownership costs. It can compare petrol with diesel, an EV with a combustion car, or two vehicles of the same type. Use the Car Ownership Calculator if depreciation, insurance, tax and servicing matter to the decision as well.
How the calculation works
Miles are converted to kilometres using 1 mile = 1.609344 km. UK mpg uses 4.54609 litres per gallon; US mpg uses 3.785411784. For mpg, litres per kilometre = litres per gallon ÷ (mpg × 1.609344). For L/100 km, divide consumption by 100. Multiply litres by the entered fuel price. For an EV, battery kWh per kilometre = kWh/100 km ÷ 100. Electricity bought divides that by charging efficiency ÷ 100, then multiplies by the electricity price. Set efficiency to 100% if the consumption already includes electricity measured at the charger. Annual distance multiplies each cost per kilometre.
Example
An EV using 18 battery kWh/100 km with 90% charging efficiency buys 20 kWh per 100 km. At an illustrative £0.25/kWh, its energy costs £5 per 100 km. A fuel car using 5 L/100 km at £1.45/L costs £7.25 per 100 km. These are chosen example inputs, not model-specific consumption claims.
Practical tip
Use consumption from the kind of driving you actually do. A blended home/public charging price should reflect the share of energy you buy at each rate.
Frequently asked questions
Can I compare petrol and diesel without an EV?
Yes. Choose a fuel-economy measure for both vehicles and enter each fuel price. The same distance is used for both.
Why does UK mpg differ from US mpg?
The two measurements use different gallon sizes. Choose the convention used by your consumption figure rather than entering a UK figure in the US option.
Does the cheaper energy result mean the car is cheaper to own?
Not necessarily. Purchase price, depreciation, insurance, tax, maintenance and charging-session fees are outside this comparison. Use the ownership tool to include those costs.