Electric Car Charging Cost Calculator
Enter your EV's efficiency, your electricity price and your driving to see charging costs per trip and per year, and the saving against a petrol car.
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Formula
- Battery use per km:
kWh/100 km ÷ 100,kWh/100 mi ÷ 100 ÷ 1.609344,1 ÷ (mi/kWh × 1.609344)or1 ÷ (km/kWh). Energy from the grid = battery use ÷ charging efficiencyCharging cost = distance × energy from the grid per km × price per kWh- Petrol cost for the same distance:
distance × L/100 km ÷ 100 × price per litre(mpg and gallon prices are converted with 1 US gal = 3.785411784 L, 1 UK gal = 4.54609 L, 1 mi = 1.609344 km). Saving = petrol cost − charging cost
Worked example
18 kWh/100 km at 90% charging efficiency draws 0.18 ÷ 0.90 = 0.20 kWh per km from the grid. A 100 km trip is 20 kWh, costing 20 × 0.30 = 6.00; 15,000 km a year is 3,000 kWh and 900.00. A petrol car at 7 L/100 km and 1.80 per litre costs 12.60 per trip and 1,890.00 a year, a saving of 990.00 a year.
Frequently asked questions
How much does it cost to charge an electric car?
Multiply the energy used by the price per kWh. An EV using 18 kWh/100 km over 100 km uses 18 kWh at the battery, or 20 kWh from the grid at 90% charging efficiency, which costs 6.00 at 0.30 per kWh.
What is charging efficiency?
Some energy is lost as heat while charging, so you pay for more than reaches the battery. At 90%, 18 kWh into the battery needs 18 / 0.90 = 20 kWh from the socket. Home charging is often 85% to 92%.
How do I convert miles per kWh to kWh per 100 km?
Divide 62.1371 by miles per kWh. At 4 miles per kWh that is 15.53 kWh/100 km. In miles, 100 miles at 4 miles per kWh uses 25 kWh.
How is the saving against a petrol car calculated?
The calculator prices the same distance for a petrol car from its economy and fuel price, then subtracts the EV cost. 15,000 km at 7 L/100 km and 1.80 per litre is 1,890.00 for petrol against 900.00 for the EV, a saving of 990.00. Public fast chargers cost more, so use your own average electricity price.