EV charging-cost formulas
Charging efficiency = 1 − the charging-loss percentage.
A 20% to 80% session adds 60% of the usable battery capacity before charging losses are included.
Use a weighted charging price for the annual budget
One low overnight tariff does not describe a driver who regularly uses rapid public charging. Estimate the share charged at home, work and public stations, then weight the different prices. Time-of-use tariffs and session fees can also change the amount actually paid.
Compare EV and petrol costs over the same distance
Energy cost is only one part of the decision. Keep annual mileage and ownership period identical, then add purchase price, finance, insurance, servicing and depreciation with the electric versus petrol cost calculator and the total car cost calculator.
Sources and checks
AutoPrisme uses the figures you enter. The links below explain the rule, market context or consumer protections used to frame this calculator. Always verify the numbers in your own quote or contract.
- US Department of Energy — Charging electric vehicles at homeOfficial explanation of EV cost per mile using kWh consumption and electricity price.
- US Department of Energy — Vehicle Cost Calculator methodologyOfficial methodology for converting energy use and energy prices into annual vehicle costs.
- FuelEconomy.gov — All-electric vehiclesOfficial US information about EV efficiency, batteries and charging considerations.
Frequently asked questions
How do I calculate the cost of charging an electric car?
Multiply the grid energy used by the electricity price per kWh. For driving cost, divide distance by 100, multiply by the vehicle's kWh-per-100-distance figure, allow for charging losses and then apply the price per kWh.
How much does it cost to charge an EV from 20% to 80%?
Multiply usable battery capacity by 60%, adjust for charging losses and multiply the grid energy by your electricity price. The calculator performs those steps with your own battery and tariff.
Should I include charging losses?
Yes when you want the amount billed by the electricity supplier. Energy drawn from the grid can be higher than the energy stored in the battery. The real difference varies with the vehicle, charger, temperature and charge rate.
Should I use my home or public charging price?
Use the price that matches the charging session. For an annual estimate, calculate a weighted price from your expected home, workplace and public charging mix rather than using the cheapest tariff for every kWh.