This estimator calculates how long an electric vehicle needs to recharge energy previously exported to a home, building, or grid through vehicle-to-grid operation. It accounts for the exported energy, charger power, charging efficiency, and any additional reserve energy you want to restore.
The result is useful for planning when the vehicle must be ready again after a V2G event. It separates energy drawn from the grid from energy actually stored in the battery, making charging-loss assumptions visible.
1. Enter exported energy
Use the battery energy delivered during the V2G session.
2. Add a reserve target
Include extra energy if the vehicle should finish above its pre-event level.
3. Enter available charging power
Use the sustained AC or DC charging power, not only the charger nameplate maximum.
4. Set charging efficiency
Include conversion and battery losses as a percentage.
5. Check readiness time
Use the estimated hours to schedule a recharge before the next trip.
Efficiency is entered as a percentage and converted to a decimal. The model assumes constant charging power.
The main result is the estimated plug-in time needed to replace exported and reserve energy.
Actual charging may slow near a high state of charge or when battery temperature limits power.
Given: 12 kWh exported, 3 kWh extra reserve, 7.2 kW charging power, and 90% efficiency.
Calculation: Battery energy = 15 kWh. Grid energy = 15 ÷ 0.90 = 16.67 kWh. Time = 16.67 ÷ 7.2 = 2.31 hours.
Result: Allow about 2.31 hours of charging.
Use battery-side exported energy when available. If you only have meter data, keep the measurement basis consistent with the efficiency assumption.
A reserve allows the vehicle to finish the recharge with more energy than it had immediately before the V2G event.
Not always. Power may taper at high state of charge or change with temperature and site load limits.
The recharge side is represented by charging efficiency. Export-side losses should already be reflected in the exported-energy figure or modeled separately.
Multiply the decimal part by 60. For example, 2.31 hours is about 2 hours and 19 minutes.