EV Charging Time Calculator
Estimate electric-vehicle charging time, wall energy, charging cost, current and range added from battery and charger inputs.
Default project preview
7.64 hours
Battery energy added
45 kWh
Wall energy
50 kWh
Range added
180 miles
Approximate current
30 A
Calculator
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Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Usable battery capacity
Enter this project assumption in kWh. The current imperial default is 75 kWh.
Starting charge
Enter this project assumption in %. The current imperial default is 20 %. Minimum: 0. Maximum: 100.
Target charge
Enter this project assumption in %. The current imperial default is 80 %. Minimum: 0. Maximum: 100.
Charger power
Enter this project assumption in kW. The current imperial default is 7.2 kW.
Charging efficiency
Enter this project assumption in %. The current imperial default is 90 %. Minimum: 1. Maximum: 100.
Taper and overhead allowance
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 50.
Supply voltage
Enter this project assumption in V. The current imperial default is 240 V.
Estimated full-charge range
Enter this project assumption in miles. The current imperial default is 300 miles. Minimum: 0.
Electricity price
Enter this project assumption in per kWh. The current imperial default is 0.18 per kWh. Minimum: 0.
How to read the outputs
Battery energy added
stored in battery. Default preview: 45 kWh.
Wall energy
90% efficiency. Default preview: 50 kWh.
Range added
from entered full range. Default preview: 180 miles.
Approximate current
at 240 V. Default preview: 30 A.
Base charge time
before taper allowance. Default preview: 6.94 h.
Charging cost
entered electricity rate. Default preview: $9.00.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Battery energy = capacity × charge-percent increase. Wall energy = battery energy ÷ efficiency. Time = wall energy ÷ charger power × taper allowance.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: July 30, 2026
Use this calculator to estimate EV charging time from battery energy to add, charger power and an editable charging-efficiency factor. It supports trip and equipment planning, not electrical-circuit design.
Calculation steps
- 1Calculate energy needed from battery capacity and starting/target state of charge.
- 2Apply the charger or vehicle power limit.
- 3Apply charging efficiency.
- 4Divide required battery energy by effective charging power.
Worked numerical example
Adding 45 kWh to a battery with a 7.2 kW charger at 90% efficiency gives effective battery power of 6.48 kW, so estimated time is about 6.94 hours.
Purchasing and rounding
EVSE is selected in available current and power ratings. The vehicle onboard charger and circuit capacity can limit actual power below the EVSE label.
Interpret the result
Charging slows if the vehicle reduces power near high state of charge or because of temperature. The result is an average-time estimate.
Page-specific assumptions
- Constant average charging power.
- Efficiency is representative.
- No charging taper unless reflected in efficiency.
- Battery capacity refers to usable energy.
Common mistakes
- Using EVSE maximum when the vehicle accepts less.
- Ignoring charging losses.
- Confusing kW and kWh.
- Sizing circuits from calculator output without an electrician.
Primary and technical references
BuildMeter provides planning estimates, not engineering, architectural, electrical, mechanical, plumbing, permit or code approval. Review the methodology and verify final decisions with product documentation and qualified professionals.
FAQ
EV Charging Time Calculator questions
Why is wall energy greater than battery energy?+
Charging electronics, battery conditioning and other losses mean more energy is drawn from the supply than is stored.
Why does charging slow near a high state of charge?+
Many vehicles reduce charging power as the battery fills to control heat and protect battery health.
Does charger nameplate power guarantee that rate?+
No. The vehicle onboard charger, supply circuit, temperature and charging session can limit actual power.