EV Charging Time Calculator
This EV charging time calculator estimates how long it takes to charge an electric vehicle from a given state of charge to a target level, based on the battery capacity in kWh, the charger's power output in kW, and charging efficiency losses. Electric vehicle owners use this formula daily to plan charging sessions around travel schedules, overnight charging windows, and peak electricity rate hours. The DOE's Alternative Fuels Data Center and manufacturer guidance informed the efficiency factors used here.
EV charging time formula
kWh needed = Battery (kWh) * (Target SoC% - Current SoC%) / 100 Charging time (hr) = kWh needed / (Charger kW * Efficiency)
Efficiency accounts for heat losses in the on-board charger and cables. Level 2 AC charging is typically 85-92% efficient. DC fast charging bypasses the on-board charger and is 90-95% efficient at the charger itself but battery acceptance rate limits apply near 80% SoC.
Charger power reference
- Level 1 (120V / 12A): approximately 1.44 kW.
- Level 2 (240V / 32A): approximately 7.68 kW. This is the most common home EVSE.
- Level 2 (240V / 48A): approximately 11.52 kW. Faster Level 2 option.
- DC Fast Charger (CCS/CHAdeMO): 50 to 350 kW. Limited by vehicle's maximum acceptance rate.
- Tesla Supercharger V3: up to 250 kW peak delivery.
Frequently asked questions
How long does it take to charge an electric vehicle?
Charging time depends on battery capacity (kWh) and charger power (kW). A Level 1 (120V/12A) charger delivers about 1.4 kW, taking 40-80 hours for a full charge on a large EV. A Level 2 (240V/32A) delivers 7.7 kW, taking 8-12 hours. A DC fast charger (50-350 kW) can add 100-200 miles in 20-45 minutes.
What is the difference between kW and kWh?
kW (kilowatts) is the rate of power delivery. kWh (kilowatt-hours) is the amount of energy stored or delivered. A 7 kW charger running for 3 hours delivers 21 kWh of energy. A 75 kWh battery is a fixed capacity; the charge rate depends on the charger's kW rating.
What is charging efficiency?
Not all power from the grid reaches the battery. AC chargers lose 10-15% to heat in the on-board charger. DC fast chargers lose 5-10%. The calculator uses a user-adjustable efficiency factor; 0.90 (90%) is typical for Level 2 AC charging.
Should I charge to 100% every time?
Most EV manufacturers and battery experts recommend daily charging to 80% to preserve battery longevity, reserving 100% charges for long-distance days. Lithium-ion batteries experience accelerated degradation when held at 100% state of charge for extended periods.
What charger level should I install at home?
A Level 2 EVSE (240V, 32-50A) is the most practical home charging solution for most EVs. It restores 20-30 miles of range per hour. Level 1 (120V) is adequate only for plug-in hybrids or vehicles driven less than 30 miles per day.
Official sources
- US DOE Alternative Fuels Data Center: afdc.energy.gov - EV charging levels and times.
- US DOE Energy Efficiency: energy.gov - EV range and charging data.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.