Energy
Estimate how long a charge will take from your battery size and charger power.
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EV charging time calculator guide
Charging time depends on the energy you need to add, the power the charger can deliver, and the efficiency of the charging path between the wall and the battery cells. This calculator takes battery capacity, the percentage of the pack you are adding, the charger’s power rating, and a charging efficiency, then divides the energy needed by the usable power to give an estimated duration in hours. It separates the battery energy from the grid energy so a power rating is not mistaken for the amount stored, and it shows the usable charging power after losses on its own row. The estimate assumes the charger runs flat out for the whole session, which is realistic for Level 2 AC charging up to about 80–90% state of charge but optimistic for DC fast charging, where the vehicle tapers power sharply as the battery fills. Use it to plan overnight charging, compare a 7 kW and an 11 kW home unit, or estimate how long a public stop will take.
Energy delivered (kWh) = battery capacity × charge added ÷ 100. Usable charging power (kW) = charger power × (efficiency ÷ 100). Charging time (h) = energy delivered ÷ usable charging power.
Worked example with the defaults: a 75 kWh battery receiving a 50% charge needs 75 × 50 ÷ 100 = 37.5 kWh of energy delivered to the pack. An 11 kW charger at 90% efficiency provides 11 × 0.90 = 9.9 kW of usable charging power, because roughly a tenth of the wall power is lost as heat. Dividing energy by power gives 37.5 ÷ 9.9 = 3.79 hours, which the calculator displays as 3.8 hours. On a 7.4 kW single-phase home charger the same top-up takes 37.5 ÷ (7.4 × 0.90) = 5.6 hours, and on a 2.3 kW portable cable about 18 hours.
Use kWh for battery capacity, percent for charge added and efficiency, and kW for charger power. Enter 50 for a 50 percentage-point increase, not the finishing state of charge. If a charger is rated in amps, multiply by voltage to get watts: 32 A × 230 V = 7,360 W = 7.4 kW for single-phase, or 16 A × 400 V × 1.73 = 11 kW for three-phase. The vehicle may taper power near a high state of charge, so the last 10–20% of a DC session can take as long as the first 50%.
The result is an idealized planning duration. Compare it with the vehicle’s onboard charger limit, temperature, battery state, and the actual charging curve; the real session is never shorter than this estimate and is often somewhat longer.
Do not divide the battery percentage directly by kW; percentages must be converted to kWh first, so a 50% top-up of a 75 kWh pack is 37.5 kWh, not 50 kWh. Do not use the wallbox nameplate without checking the vehicle’s onboard AC limit: an 11 kW charger feeding a car with a 7.4 kW onboard charger delivers 7.4 kW at most. Do not assume the final few percent charge at the average rate, especially on DC fast chargers, and do not ignore cold weather, which slows charging until the battery warms. Finally, the efficiency field wants a realistic 85–92% for AC charging, not 100%.
Confirm equipment limits and electrical installation requirements with the vehicle and charger documentation.
Sources
How it works
Estimate how long a charge will take from your battery size and charger power. This tool explains the calculation so you can adjust the assumptions to match your situation.
Worked example
With Battery size = 75 kWh · Charge added = 50 % · Charger power = 11 kW · Charging efficiency = 90 % → 3.8 hours (estimated charging time). Change an input above and this example updates with your numbers.
Common questions
Divide the energy you are adding by the charger’s usable power. Adding 50% to a 75 kWh battery on an 11 kW charger at 90% efficiency takes about 3.8 hours; the vehicle may charge more slowly near a high state of charge or in cold weather.
No. Vehicle onboard-charger limits, supply limits, temperature, state of charge, and load management can reduce the actual power. Many cars accept only 7.4 kW on AC, in which case an 11 kW wallbox charges no faster than a 7.4 kW one.
A 7.4 kW home charger adds about 6.7 kWh per hour after losses, so an eight-hour overnight window replaces about 53 kWh, or roughly 70% of a 75 kWh battery. Most daily driving of 30–50 miles needs only 1–2 hours of charging.
The estimate assumes full charger power for the whole session. Real sessions lose time to cold batteries, power tapering above 80%, shared-supply load balancing, and onboard-charger limits, and a low efficiency cable or adapter can add 10% or more.