EV Charging Time Calculator
Estimate how long it takes to charge an electric vehicle from any battery capacity, charger power and start/finish charge level. Enter the pack size in kWh, the charger's kW and (optionally) your start and target state-of-charge — a browser-only estimate for home, work and public charging.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter your EV's usable battery capacity in kWh.
- Enter the charger power in kW (e.g. 2.4 kW granny lead, 7 kW or 11 kW home wallbox, 50 kW+ DC fast charger).
- Leave charging efficiency at 0.9 or adjust it, then optionally set the start and end state-of-charge percentages (defaults are 0% to 100%).
- Read the charging time in hours-and-minutes, the energy required and the charge added per hour.
How it works
First the energy to add is the pack size scaled by how much charge you want: energy = capacity × (end% − start%) ÷ 100. Then time = energy ÷ (charger power × efficiency). The efficiency term (0.9 by default) accounts for losses in the charger and battery, so a 7 kW charger effectively delivers about 6.3 kWh into the pack each hour. The decimal-hour result is converted to hours and minutes. This is a constant-power estimate: AC home charging stays close to constant power, but DC fast charging tapers above about 80%, so real rapid-charge times to a full battery are longer than the simple formula suggests.
Worked example
Worked example. A 60 kWh EV on a 7 kW home charger at 90% efficiency, going from 20% to 80%: energy = 60 × (80 − 20) ÷ 100 = 36 kWh. Time = 36 ÷ (7 × 0.9) = 36 ÷ 6.3 = 5.714 hours ≈ 5 h 43 min, adding about 6.3 kWh per hour.
Common mistakes
- Using 100% efficiency — charging losses mean the pack receives roughly 85–92% of the charger's rated power, so ignoring efficiency underestimates the time.
- Assuming DC fast charging holds full power to 100% — charging slows sharply above about 80%, so a constant-power estimate is optimistic for the last stretch.
- Entering the charger's rated kW when the car's on-board AC charger is the real limit — a 22 kW AC point still only charges as fast as the vehicle's on-board charger (often 7 or 11 kW) allows.
Frequently asked questions
Why does a 7 kW charger not add 7 kWh per hour?
Charging is not 100% efficient — energy is lost as heat in the charger and battery. At 90% efficiency a 7 kW charger adds about 6.3 kWh to the pack each hour, which is why the time is a little longer than capacity ÷ power alone.
Why is my real DC fast-charge time longer than this estimate?
DC fast chargers taper the current above roughly 80% state-of-charge to protect the battery, so the last 20% is much slower than constant power. Charging from a low to a moderate state-of-charge matches this estimate best; charging to 100% takes disproportionately longer.
What efficiency should I use?
0.85–0.92 is typical; 0.90 is a good default. Slow AC charging in the cold sits at the lower end because more energy runs battery heating and conditioning; warm, higher-power charging is nearer the top.
Related tools
- Electricity Cost Calculator
- Solar Output Calculator
- Battery Bank Size Calculator
- Solar Panel Count Calculator
- Solar Charge Controller Size Calculator
- Solar Irradiance to kWh Calculator
Explore more in Electrical, Electronics, Solar & Energy.
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.