EV Charging Cost Calculator
Calculate what it costs and how long it takes to charge an electric car.
Please note: Estimates for planning only. Real fuel economy, depreciation, insurance and lease terms vary widely by vehicle, region and driving style. Confirm figures against a dealer quote or your own records before relying on them.
What the EV Charging Cost Calculator does
Charging cost is the energy your battery needs, grossed up for charging losses, multiplied by your electricity rate. Time is the energy divided by the charger’s power — though real sessions slow considerably above 80% state of charge, which the simple calculation does not capture.
Formula
Energy to battery = Capacity × (Target% − Start%) ÷ 100Energy from grid = Energy to battery ÷ Charging efficiencyCost = Energy from grid × RateTime = Energy to battery ÷ Charger power
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Battery capacity | kWh | Yes | Accepts more than 0. |
| Starting charge | % | Yes | — |
| Target charge | % | Yes | — |
| Electricity rate per kWh | selected currency | Yes | Accepts 0 or more. |
| Charger power | kW | Yes | Accepts more than 0. |
| Charging efficiency | % | Yes | Energy lost as heat in the charger and battery. |
| Vehicle efficiency | number | Optional | Accepts 0 or more. |
| Efficiency measured in | one of 4 options | Yes | — |
| Currency | one of 10 options | Optional | — |
How to use it
- Choose Efficiency measured in and Currency.
- Enter Battery capacity, Starting charge, Target charge and Electricity rate per kWh and 2 more.
- Optionally add Vehicle efficiency.
- Select Calculate.
Worked example
A 75 kWh battery from 20% to 80% on a 7.4 kW wallbox at $0.15/kWh, 90% efficient.
- Battery
- 75 kWh
- From
- 20%
- To
- 80%
- Rate
- $0.15
- Charger
- 7.4 kW
45 kWh into the battery, 50 kWh drawn from the grid — $7.50, taking 6 h 5 min.
Reading the result
- "Cost per kWh delivered to the battery" is the real effective price once charging losses are folded in — always higher than the entered rate, by exactly the efficiency loss.
- The charger-speed table isn't adjusted for the notes' 80% tapering caveat — a charge that crosses that threshold on a fast charger will genuinely take longer than the table's simple division suggests.
Assumptions and limitations
- Charging efficiency is applied as one flat percentage for the whole session, which is most accurate for a charge that stays below the 80% mark where real tapering begins — like the 20%→80% example itself.
- The vehicle-efficiency conversion, when entered, treats kWh/100km as constant regardless of speed, temperature or terrain.
Common mistakes
- Using the simple time formula for a charge that crosses 80% on a fast charger — real charging tapers sharply past that point, per the notes and FAQ.
- Comparing charging cost against a fuel fill-up without accounting for charging losses — "cost per kWh delivered," not the flat rate, is the fair basis for a per-mile comparison against gas.
Frequently asked questions
Why do I pay for more energy than the battery holds?
Charging is not perfectly efficient. Roughly 10% is lost as heat in the charger and battery, and your meter records all of it.
Why does the last 20% take so long?
Charging power tapers steeply above 80% to protect cell life. That is why rapid-charging advice is usually to stop at 80% and drive on.