Enrichment · Passion Projects · Vehicles

What it really costs
to charge the car.

Type your miles, the car’s efficiency and your electricity prices. The calculator counts the energy, adds what is lost while charging, splits home from public charging and compares the month with gas.

Price the chargingWhat you get

The charging cost calculator

The worked example is a made-up compact EV driven 1,000 miles a month; the prices are examples, not current rates. Nothing you type leaves this browser.

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What you get

Enrichment · Passion ProjectsFree

What you finish with
kWh used, monthly and yearly charging cost, cost per mile, the home and public split, and the gasoline comparison. It prints as a summary and downloads as a spreadsheet.
Who it is for
Families and students weighing an electric car, drivers budgeting for charging, and consumer math and environmental science classes.
Format
Browser calculator for a phone, tablet or computer, by touch or keyboard. Prints a summary; downloads a spreadsheet (.csv); export and import a file.
Access
Free. No account, no sign-in and nothing to install. Everything you type stays in this browser; nothing is sent to Caveat.
Where it lives
The Passion Projects space in Caveat Enrichment.
Support
Questions, a correction or a request: team@caveatacademic.com.

How to use it

  1. Estimate your miles a month from the odometer.
  2. Find the car’s miles per kWh on its trip screen or EPA label.
  3. Type your electricity price from a bill.
  4. Add the public fast-charging price and share, if any.
  5. Add a gas car to compare.

Price the charging

How the charging cost is worked out

Miles to kWh, kWh to dollars.

The worked example: a compact EV driven 1,000 miles a monthBattery energy286 kWh1,000 mi ÷ 3.5Home, at the outlet286 kWh90% of it ÷ 0.90 lossesPublic29 kWh10% at $0.48Cost$62a monthThe worked example: a compact EV driven 1,000 miles a monthBattery energy286 kWh1,000 mi ÷ 3.5Home, at the outlet286 kWh90% of it ÷ 0.90 lossesPublic29 kWh10% at $0.48Cost$62a month
Charging cost is energy times price; losses and the public share move it more than most drivers expect.

Efficiency and losses

The EPA label gives kWh per 100 miles; 29 kWh per 100 miles is about 3.4 miles per kWh. Charging is not perfectly efficient: some energy turns to heat in the charger and battery, typically 10 to 15 percent on a home Level 2 charger and more on a standard outlet. Your meter counts that energy, so the calculator adds it back.

Where prices differ

Home electricity is billed per kWh, sometimes cheaper overnight on a time-of-use plan. Public fast chargers usually cost two to four times as much per kWh. A driver who charges mostly at home pays far less per mile than one who relies on fast charging, which the table shows line by line.

Sources

  1. U.S. Department of Energy and U.S. Environmental Protection Agency. fueleconomy.gov: electric vehicle efficiency labels and cost estimates (fueleconomy.gov).
  2. U.S. Department of Energy, Alternative Fuels Data Center. Charging electric vehicles at home and in public (afdc.energy.gov).
  3. U.S. Energy Information Administration. Average retail price of electricity and gasoline prices (eia.gov).
  4. Idaho National Laboratory. Level 2 charging efficiency testing (inl.gov).

The worked example and its prices are made up. Check your own bill and charging network for current prices. Your entries stay in this browser. Support: team@caveatacademic.com.