Charging
EV Charging Calculator
Price one charging session and estimate how long it takes. Enter energy delivered to the battery, an efficiency loss, your electricity rate, and charger power. This is not a gas-versus-electric decision page.
Numbers stay in this browser. EnergyToolMage does not upload your inputs or require an account.
Formula
efficiency = (100 − loss%) ÷ 100; grid_kWh = delivered_kWh ÷ efficiency; cost = grid_kWh × USD/kWh; hours = delivered_kWh ÷ (charger_kW × efficiency)
Assumptions
- Charger kW is constant.
- Loss percent covers the whole path you care about (EVSE + onboard charger).
- No idle fees, demand charges, or DC-fast premiums unless you raise the rate.
How it works
Loss percent becomes efficiency. Grid energy is delivered energy divided by efficiency, because losses happen on the way into the battery. Time uses delivered energy divided by charger kW times efficiency.
Inputs and results
Inputs: delivered kWh, loss %, USD/kWh, charger kW. Outputs: grid kWh, USD, hours.
Worked examples
60 kWh delivered, 10% loss, $0.16/kWh, 7.2 kW
Efficiency 0.90. Grid energy 66.666667 kWh. Cost $10.67. Time 9.259 hours.
How to use this calculator
- Enter kWh added to the battery.
- Enter charging loss percent (example 10 is an assumption, not a measurement).
- Enter your electricity rate and the charger’s kW.
- Read grid kWh, session cost, and hours.
Limitations
- Does not compare gasoline and electric vehicles.
- Does not price a home charger installation.
- Does not model preconditioning or cold-weather range loss beyond the loss % you enter.
Sources and freshness
- Every rate, wattage, hour, and loss percentage is a user input or a labeled example. Nothing here is a live utility tariff.
- The $0.16/kWh figure that appears in examples is an illustrative default, not a U.S. average and not current.
- Annualization uses 365.25 days per year and 365.25 ÷ 12 days per month. Your billing cycle will differ.
- Default 10% charging loss is a DEFAULT_ASSUMPTION / EXAMPLE_ONLY value, not an external measurement.
Questions
Is the 10% loss a measured fact?
No. It is a labeled example assumption. Level 2 losses often land around that neighborhood, but temperature, the vehicle, and the charger change the number. Enter your own estimate.
Do I enter battery size or energy added?
Enter the kilowatt-hours you want to add, not necessarily the full pack. A 10% top-up of a 75 kWh pack is 7.5 kWh delivered.
Does this say whether an EV is cheaper than gasoline?
No. That is a side-by-side decision with miles, MPG, and a fuel price. This page only prices and times a charge.
Related energy tools
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- Electricity costMultiply energy you already know in kilowatt-hours by the dollars-per-kWh on your bill. Use this when a meter, EnergyGuide label, or another calculator already gave you kWh.
- Appliance costUse this when you know an appliance’s watts and how often you run it. The page annualizes with a disclosed calendar convention and your bill rate.