How to use the ev charging cost calculator
- Choose to work by miles driven or by battery charge added.
- Enter the miles and your car's efficiency in kWh per 100 miles, or the battery size and the start and end charge levels.
- Enter your electricity price per kWh and the charging losses. Both defaults are examples.
- Optionally add a gas car's mileage and fuel price to compare, and the miles you drive in a year to see the yearly cost.
Formula
Energy into the battery = miles x kWh per 100 miles / 100, or battery kWh x (end % - start %)
Energy from the outlet = energy into the battery / (1 - losses)
Cost = energy from the outlet x price per kWh
Cost per mile = cost / miles; gas car cost per mile = fuel price / mpg
Charging losses are the energy lost as heat in the charger, the cable and the battery. The default of 10 percent is an example.
Worked example
Driving 1,000 miles at 30 kWh per 100 miles takes 300 kWh into the battery. With 10% losses you draw 333.33 kWh from the outlet, and at $0.17 per kWh that costs $56.67, or $0.0567 a mile.
Charging a 75 kWh battery from 20% to 80% adds 45 kWh, draws 50 kWh from the wall and costs $8.50, which is about 150 miles of range at the same efficiency. A gas car at 28 mpg and $3.50 a gallon spends $125.00 for the same 1,000 miles, so the EV saves $68.33.
Home charging versus public charging
Home charging uses your utility rate, which may change by time of day. Public fast chargers are usually priced per kWh or per minute and cost more than home power. To check public charging, enter the price shown at the charger, and consider any idle or session fees separately. Enter the cost per kWh for the way you charge most often.
What changes efficiency
Efficiency varies with speed, temperature, terrain, cargo and use of heating or cooling. Highway driving in cold weather can use much more energy than city driving in mild weather. Use the figure from your own car's display over a few weeks for the best results, rather than a published average.
Related tools
Compare fuel costs with the fuel cost calculator and the MPG calculator, see electricity costs for other devices in the electricity cost calculator, and weigh purchase price and running costs with the total cost of car ownership calculator.
Assumptions and limits
- The electricity price, the efficiency and the charging losses are example values you should replace with your own.
- Efficiency is the same for all the miles you enter.
- Time-of-use rates, demand charges, public charger fees and battery wear are not modeled.
- The gas car comparison uses the fuel price and mileage you enter and ignores maintenance differences.
Frequently asked questions
How much does it cost to charge an electric car?
Multiply the kWh drawn from the outlet by your price per kWh. A 75 kWh battery charged from 20 to 80 percent at $0.17 costs about $8.50 with the default 10 percent charging losses.
How do I find my car's efficiency?
Many cars show kWh per 100 miles or miles per kWh on the trip display. Divide 100 by miles per kWh to get kWh per 100 miles.
Why do I pay for more energy than the battery receives?
Some energy is lost as heat while charging. The amount depends on the charger, the temperature and the battery.
Is charging cheaper than gas?
Often, but not always. It depends on your electricity rates, where you charge and your gas price. Enter both to compare.