EV Charging Time Calculator
Estimate the time required to charge your battery from X% to Y%.
Last Updated: January 2026
What this calculator does
Estimate how long an EV charge session will take from a starting state of charge to a target level. It uses battery capacity, charger power, vehicle acceptance limits, and charging losses to compute time, energy added, and grid energy used. This is useful for home charging plans and for comparing public charging options.
Inputs explained
- Battery capacity: Total or usable capacity in kWh.
- Start level: Current state of charge as a percent.
- Target level: Desired state of charge as a percent.
- Charger power: Charger output in kW.
- Vehicle max acceptance: Optional kW limit the vehicle can actually accept.
- Charging efficiency loss: Percent of power lost to heat and conversion.
How it works / Method
- Choose the lower of charger power and vehicle max acceptance as effective power.
- Apply charging loss to estimate net power that reaches the battery.
- Compute energy needed from start to target as a percent of capacity.
- Divide energy needed by net power to estimate time.
- Multiply effective power by time to estimate grid energy used.
Formula(s) used
effective_power = min(charger_power, vehicle_max)
net_power = effective_power * (1 - loss%/100)
energy_needed = capacity_kWh * (target% - start%)/100
time_hours = energy_needed / net_power
grid_energy = effective_power * time_hours
Units: power in kW, energy in kWh, time in hours. Assumes steady charging power during the session.
Inputs
Results
Est. Charging Time
-
Energy Added to Battery
-
Effective Charging Power
-
Grid Energy Used (est.)
-
Step-by-step example
Example inputs: 75 kWh battery, start 10%, target 80%, charger power 7.2 kW, vehicle max 11 kW, and 10% loss.
- Energy needed: 75 * (80 - 10) / 100 = 52.5 kWh.
- Effective power: min(7.2, 11) = 7.2 kW.
- Net power to battery: 7.2 * 0.90 = 6.48 kW.
- Time: 52.5 / 6.48 = 8.10 hours (about 8h 6m).
- Grid energy: 7.2 * 8.10 = 58.3 kWh.
Use cases
- Plan overnight Level 2 charging time at home.
- Compare Level 1, Level 2, and DC fast charging sessions.
- Estimate how long a public charging stop may take.
- Test how a lower vehicle acceptance rate affects charging time.
- Estimate grid energy for cost or emissions calculations.
- Plan charging around time of use electricity windows.
Assumptions & limitations
- Charging power is treated as constant; real sessions often taper at higher state of charge.
- Battery conditioning, temperature, and preheating can change effective power.
- Loss percent is simplified and does not vary with charge rate or temperature.
- Start and target levels must be within 0 to 100% and target must be higher than start.
- Does not model idle fees or station limits at public chargers.
- Results are estimates for planning, not a guaranteed session time.
Disclaimer: Results are estimates for planning only. Real world charge time varies by vehicle, charger, and conditions.
Frequently Asked Questions
As the battery fills, the vehicle reduces power to protect the cells and manage heat. This
charging taper is common for DC fast charging and can also appear on AC charging at high state
of charge. The calculator assumes a steady average power, so real sessions may take longer
near the top of the battery. For faster trips, many drivers stop around 80% and resume driving.
If your vehicle lists usable capacity, use that value because it represents the energy you can
actually charge into and drive from. Some manufacturers list total pack size while reserving a
buffer that is not accessible. If you only know total capacity, the calculator still works, but
the time estimate may be slightly optimistic. You can adjust by reducing capacity to reflect
the usable portion.
The vehicle max acceptance is the highest charging power your EV can take at that moment. If a
charger is rated higher than your vehicle limit, your EV will cap the power to protect the
battery. This is why a 150 kW charger might only deliver 80 kW to some vehicles. Entering the
max acceptance gives a more realistic estimate of charging time.
Losses cover AC to DC conversion, thermal management, and electronics overhead. A typical range
for home AC charging is single digits to low teens percent, while fast charging can vary. If you do not
know the exact value, 10% is a reasonable planning estimate. You can also compare results with
your vehicle energy screen to refine the number over time.
It provides a useful estimate, but DC fast charging power changes continuously. Many vehicles
start at high power and then taper as state of charge increases, so the average power is lower
than the peak rating. To approximate a fast charge, enter a realistic average power from your
last session or use a lower effective power than the charger nameplate rating.
The grid energy includes losses that occur between the wall and the battery. Energy is lost as
heat in the onboard charger, cabling, and thermal management systems. That is why the grid kWh
is higher than the kWh added to the pack. The difference grows if you charge in very hot or cold
conditions or use fast charging very often.
Sources & references
- U.S. Energy Information Administration: Measuring electricity - Defines kW and kWh for power and energy.
- DOE Alternative Fuels Data Center: EV charging options for consumers - Charging level power ranges and typical use.
- U.S. EPA: Plug-in electric vehicle charging basics - Charging behavior and power tapering context.
- U.S. DOE: Vehicle Technologies Office fact of the week - Notes battery capacity on a usable energy basis.
- Schema.org: FAQPage, WebPage, and BreadcrumbList - Structured data definitions used on this page.