This estimator converts public charging conditions into an expected range shortfall compared with an ideal charging stop. It compares the energy you planned to receive with energy actually delivered after efficiency, early disconnection, or reduced charger output.
The tool is useful for drivers deciding whether they need another stop, whether a shorter session still covers the next leg, or how much buffer to preserve. It expresses the shortfall in both kilowatt-hours and miles using the vehicle’s energy consumption. Weather, speed, elevation, and accessory use can create additional real-world range variation.
1. Enter planned energy
Use the energy you expected the stop to add.
2. Enter actual charger energy
Use the session total reported by the charger.
3. Set charging efficiency
This converts wall energy into battery energy.
4. Add vehicle consumption
Enter expected consumption in kWh per 100 miles for the next leg.
5. Review the shortfall
Compare planned and actual added range.
Usable planned energy = Planned charger energy × Efficiency
Usable actual energy = Actual charger energy × Efficiency
Added range (miles) = Usable energy ÷ Consumption × 100
Range loss = Planned added range − Actual added range
The main result is the estimated miles of added range not obtained relative to the planned session.
The result is not loss of permanent battery capacity; it is a trip-level charging shortfall.
Given: Planned 45 kWh, actual 38 kWh, 92% efficiency, and 30 kWh/100 mi consumption.
Calculation: Planned usable energy = 45 × 0.92 = 41.4 kWh. Actual usable energy = 38 × 0.92 = 34.96 kWh. Planned range = 41.4 ÷ 30 × 100 = 138.0 mi. Actual range = 34.96 ÷ 30 × 100 = 116.5 mi.
Result: Range loss = 138.0 − 116.5 = 21.5 miles.
The session delivered about 6.44 kWh less usable energy than planned.
No. This calculator measures a charging-session shortfall, not long-term battery degradation.
Use charger-reported energy if that is what you have, then apply efficiency. If your vehicle reports energy added directly to the battery, set efficiency to 100%.
Use an expected value for the upcoming route, not only the vehicle’s official rating. Cold weather, high speed, and climbing can raise consumption.
If actual energy exceeds planned energy, the calculator reports zero range loss rather than a negative shortfall.
The calculator does not prescribe a buffer. Add a margin appropriate for route uncertainty, charger availability, and weather.