EV Charging Cost Calculator

How EV charging cost is calculated

An electric car's battery is measured in kilowatt-hours (kWh), the same unit as your electricity bill. To find the cost of a charge, work out how many kWh go into the battery, add the energy lost as heat in the charger and battery, and multiply by your price per kWh. Charging losses are commonly around 10% for home Level 2 charging and can be higher on a standard outlet or in cold weather.

kWh into the battery = battery kWh × (end % − start %)
kWh from the grid = kWh into the battery ÷ (1 − loss)
Cost = kWh from the grid × price per kWh
Cost per mile = price ÷ (1 − loss) ÷ miles per kWh

Worked example: charging at home

A car with a 75 kWh battery charges from 20% to 80% at home for $0.17 per kWh with 10% charging loss on a 7.2 kW charger. It drives 3.5 miles per kWh.

• Energy into the battery: 75 × 60% = 45 kWh; from the grid: 45 ÷ 0.9 = 50 kWh.
• Cost of the charge: 50 × $0.17 = $8.50. Time: 50 ÷ 7.2 ≈ 6.9 hours.
• Range added: about 158 miles; cost per mile: about $0.054 ($5.40 per 100 miles).
• Driving 1,000 miles a month costs about $53.97. A 30 mpg gas car at $3.50 a gallon would cost $116.67, so the EV saves about $62.70 a month.

Public fast charging changes the picture

Public DC fast chargers often cost much more per kWh than home electricity. At $0.40 per kWh, the same 20–80% charge costs $20.00 and 1,000 miles costs about $126.98, slightly more than the 30 mpg gas car in the example. Most EV owners who charge mainly at home, especially on a cheaper overnight rate, see the biggest savings.

Metric example (UK)

At £0.25 per kWh, 6 km per kWh and 1,500 km a month, the same 45 kWh charge costs £12.50 and the month's driving about £69.44. A petrol car doing 15 km per litre at £1.45 a litre would cost £145.00, so the EV saves about £75.56 a month.

Finding your car's efficiency

Your car's trip computer shows miles per kWh, km per kWh or kWh per 100 miles/km. Official ratings, such as those on fueleconomy.gov in the US, give kWh per 100 miles: divide 100 by that figure to get miles per kWh. Efficiency drops in cold weather, at high motorway speeds and with heavy loads, so use a figure that matches how you drive.

Why charge to 80%?

Many manufacturers recommend charging to about 80% for daily use to reduce battery wear, and fast chargers slow down sharply above about 80%, so public charging sessions are often 10–80% or 20–80%. Charge to 100% before long trips if your manual allows it.

Charging time

Time ≈ kWh from the grid ÷ charger power. A 7.2 kW home charger adds about 50 kWh in 7 hours; a standard 120 V outlet (about 1.4 kW) would take more than a day for the same energy. The car's onboard charger can limit AC charging speed, and DC fast charging slows as the battery fills, so treat the time as an estimate.

Monthly and yearly budget

Enter your typical monthly distance to turn the cost per mile or km into a monthly figure. Add any fixed costs of home charging, such as a charger installation or a separate EV tariff's standing charge, when you compare totals over several years.

Common mistakes

• Forgetting charging losses. The grid supplies more than the battery receives.
• Using the full battery size for every charge. Few people charge from 0% to 100%.
• Comparing home electricity with public charging prices. Use the price you actually pay most of the time.

Estimates only. Your utility bill, charger app and car's trip computer show real figures.

Frequently asked questions

Sources

• US Department of Energy and EPA (fueleconomy.gov). Electric vehicle efficiency ratings in kWh per 100 miles.
• US Department of Energy, Alternative Fuels Data Center (afdc.energy.gov). Charging electric vehicles at home.
• Energy Saving Trust (UK). Charging electric vehicles.

Last reviewed 27 October 2026. Results are estimates; see our disclaimer.