A 7.4 kW charging session
36 kWh stored requires 40 kWh input. At 7.4 kW constant input the estimate is about 5.405 hours. A larger charger does not help while site allocation remains 7.4 kW.
Estimated charging time 5.405 h Open in the calculator
EV charging time calculator
A faster charger only helps until the vehicle or the site becomes the limit. Compare those limits and see the energy and time needed for your target charge.
7.4charger
80charge target
Charger: 7.4 kW
Vehicle: 11 kW
Site: 7.4 kW
Available power follows the lowest limit.
| Charger kW | Estimated hours |
|---|---|
| 2.3 | 17.39 |
| 3.7 | 10.81 |
| 7.4 | 5.405 |
| 11 | 5.405 |
| 22 | 5.405 |
| 50 | 5.405 |
| 150 | 5.405 |
Keep every scenario at the same AC or DC boundary. A higher charger rating cannot overcome the entered vehicle or site limit. Comparisons keep efficiency and average power fraction unchanged.
Estimated charging time
5.405h
20% to 80%; limiting power: charger and site.
Check the values to see a result.
- Energy added to the battery
- 36 kWh
- Energy at the chosen input boundary
- 40 kWh
- Average input power
- 7.4 kW
Use matching AC or DC power boundaries. Average power and efficiency are assumptions; temperature, taper and charging control can change them.
How it’s calculated
- Energy to store = usable capacity × SOC change=60 × 0.6=36 kWh
- Average input power = lowest applicable limit × average fraction=7.4 × 1=7.4 kW
- Time = stored energy ÷ efficiency ÷ average input power=36 ÷ 0.9 ÷ 7.4=5.405 h
Time = usable capacity × SOC change ÷ efficiency ÷ average input power
Adding 36 kWh takes about 5.405 hours at 7.4 kW average input power.
Tip: Use the vehicle’s AC acceptance limit for an AC charger, or its DC limit for a DC charger. They can be very different.
Use one power boundary throughout
Battery energy determines how much charge is needed; the lowest power limit determines how quickly it can arrive. A 60 kWh usable battery moving from 20% to 80% stores 36 kWh. At 90% input-to-storage efficiency it takes 40 kWh at the chosen charging input.
The instrument compares charger ratings while retaining the vehicle and site limits. Increasing charger power beyond either limit does not shorten the calculated session.
Calculate stored energy
Stored kWh = usable battery kWh × SOC change ÷ 100
Use usable capacity rather than gross pack energy. SOC is treated as a linear fraction of that capacity; the vehicle may reserve energy outside the displayed range.
Choose AC or DC
Limiting power = min(charger, vehicle, allocated site power)
For AC charging, the vehicle limit is its onboard charger acceptance. For DC charging, use DC acceptance and express site allocation at the same DC boundary. Do not compare a DC vehicle peak with an AC wallbox limit as if both described the same charging mode.
Distinguish taper from conversion loss
Average power = limiting power × average share
Efficiency converts input energy into stored energy. The average-power share describes how long the session stays below its limiting power because of taper, thermal control or interruptions. Do not subtract the same loss twice.
Estimate duration
Hours = stored kWh ÷ efficiency ÷ average input kW
Use documented or measured average power over the specific SOC window for a more realistic estimate. A peak DC charging rating is generally not a whole-session average.
EV charging time examples
Allowing for an average below the limit
The assumed average input is 35 kW. Storing 36 kWh at 95% efficiency requires about 37.895 kWh input, giving about 1.083 hours. These are illustrative DC-boundary assumptions, not a vehicle charging curve.
Estimated charging time 1.083 h Open in the calculator
Questions about EV charging time
Will a 22 kW charger charge twice as fast as an 11 kW charger?
Only if the vehicle, site and charging mode accept the extra power. An 11 kW onboard AC charger stays limited to 11 kW when connected to a 22 kW AC point.
Does a DC session use the calculated kWh from the grid?
The calculator reports energy at the selected input boundary. If that boundary is the DC output of the charger, upstream conversion and auxiliary losses increase grid energy and are outside this result.
Why not predict time from the advertised peak charging power?
Peak power can apply over only part of the SOC range. Temperature, battery conditioning, taper and site load control can lower the session average.
Limits of this result
- Enter usable battery capacity, not gross pack capacity. The SOC window is treated as a linear fraction of usable energy.
- Express all three power limits at the same boundary: AC supplied to an onboard charger or DC supplied to the vehicle. For DC charging, grid-to-charger losses are outside the model.
- Efficiency covers losses between the chosen input boundary and stored energy. The average-power fraction accounts for taper or interruptions, not those same energy losses.
- The charger comparison retains the entered vehicle and site limits. It does not imply that a vehicle supports every listed rating or AC/DC mode.