EV AC Charging Time Calculator

Estimate an AC charging session

1. Enter the battery’s usable capacity and the starting and target charge percentages. Use usable capacity rather than a larger gross capacity figure, and keep the target at or above the starting charge.
2. Enter the AC power available to this car and the vehicle’s AC charging limit. Use kilowatts for both. A DC fast-charge rating is not the same as the vehicle’s AC limit.
3. Review the efficiency assumption and estimated duration. The starting 90% value is an editable example, not a measurement of your vehicle. Check the battery energy added and estimated AC energy in the details.

What limits the charging rate?

Usable capacity multiplied by the increase in charge percentage estimates the energy added to the battery. For example, moving a 54 kWh usable battery from 20% to 80% adds an estimated 32.4 kWh.

The calculation uses the lower of available charger power and the vehicle’s AC limit. A charger labelled 22 kW does not make an 11 kW AC-limited car accept 22 kW. Shared power or a reduced setting can lower the available power further.

Efficiency describes the share of incoming AC energy that becomes stored battery energy in this model. At 90%, adding 32.4 kWh requires an estimated 36 kWh of AC energy. Losses are applied once, not added again as a separate time allowance.

Dividing estimated AC energy by the assumed steady AC power gives the duration. The same result follows by dividing added battery energy by the modelled battery-side power. A power figure already measured after losses must not be entered as incoming AC power.

Charging examples with stated assumptions

A 54 kWh usable battery going from 20% to 80%, with 7.2 kW available, an 11 kW vehicle AC limit and 90% efficiency, gives about 5 hours. It adds 32.4 kWh to the battery and takes an estimated 36 kWh from AC power.

For the same battery, charge range and efficiency, a 22 kW charger with an 11 kW vehicle limit gives about 3 hours 16 minutes. The vehicle limit controls this estimate.

Keeping the first example’s 7.2 kW power but changing efficiency to 80% gives about 5 hours 38 minutes. It models 40.5 kWh of AC energy; it does not predict how efficiency changes during a real session.

When actual charging takes longer or differs

Power and losses can change with temperature, battery conditioning, state of charge, balancing, shared supply and vehicle settings. Near a high target, especially 100%, this simple constant-power model may underestimate the time. It contains no charging curve or taper allowance.

Use this for AC planning with known inputs. It does not model DC fast charging, a vehicle’s charging curve, gross-to-usable capacity conversion, battery health, electricity prices or a clock-time arrival. Follow the vehicle maker’s charging guidance and the session’s live estimate.

Calculations in your browser

The tool calculates from the values you enter without intentionally uploading or saving them. Copy includes the current estimate and assumptions only when requested. Normal site services and consent settings remain separate.