Electric Vehicles
Charging Session Energy Calculator
Estimate battery and wall energy for a charging session. Displayed SOC changes may not perfectly track measured pack energy.
Enter compatible measurements
Record physical measurements under repeatable conditions whenever possible.
The measurement being modeled
Estimate battery and wall energy for a charging session — the calculation follows energy or power through one defined electrical setup.
Displayed SOC changes may not perfectly track measured pack energy — that condition defines when wall energy for session is comparable with another result.
Input reference points
Usable battery capacity. Usable energy represented by zero to 100 percent — for this measurement, keep the percentage basis explicit and do not mix a decimal fraction with a percent value.
Document Starting state of charge as battery percentage before charging — this means you should keep the percentage basis explicit and do not mix a decimal fraction with a percent value.
The Ending state of charge entry represents battery percentage after charging — before calculating, keep the percentage basis explicit and do not mix a decimal fraction with a percent value.
Wall-to-battery efficiency: Share of wall energy retained in the battery — a compatible entry should keep the percentage basis explicit and do not mix a decimal fraction with a percent value.
Use the EV Climate-Control Range Impact for the separate question of how to estimate how a continuous HVAC load changes EV range at an average speed.
Operating conditions outside the formula
Control software, temperature, wiring loss, battery condition, and equipment limits can alter the measured electrical result — for wall-to-battery efficiency, the page specifically expects share of wall energy retained in the battery.
For the distinct decision to find the lowest current limit among the vehicle, charging equipment, and circuit, preserve this answer and open the EVSE Current Limit.
Turning the inputs into a result
In “wall energy = usable capacity × SOC change ÷ charging efficiency,” the printed units define how each term is interpreted.
No term beyond usable battery capacity, starting state of charge, ending state of charge, and wall-to-battery efficiency is introduced in “wall energy = usable capacity × SOC change ÷ charging efficiency.”
Following one calculation through
To trace the arithmetic, start with Usable battery capacity = 68 kWh, Starting state of charge = 35%, Ending state of charge = 82%, and Wall-to-battery efficiency = 89%.
After applying the formula, the displayed results are Wall energy for session = 35.91 kWh, Battery energy added = 31.96 kWh, and Estimated session loss = 3.95 kWh.
Using the supporting measurement
Wall energy for session answers “Estimate battery and wall energy for a charging session.” The additional displays, Battery energy added and Estimated session loss, are a different view of the same entered measurements.
Preconditioning and cabin use during charging can increase wall consumption — when that condition changes, compare separate calculator runs instead of blending the inputs.
Because displayed SOC changes may not perfectly track measured pack energy, a disagreement between wall energy for session and an outside reference should trigger a review of usable battery capacity and wall-to-battery efficiency.
Before using this result
What measurement source fits Usable battery capacity when it represents usable energy represented by zero to 100 percent?
Because usable battery capacity represents usable energy represented by zero to 100 percent, use a source tied to the exact vehicle, component, and operating period described by the other fields.
How does the warning “Displayed SOC changes may not perfectly track measured pack energy” affect Wall energy for session?
The condition “Displayed SOC changes may not perfectly track measured pack energy” is not corrected automatically by the numeric inputs, so create a separate charging session energy case when it changes.
What assumption is expressed by “wall energy = usable capacity × SOC change ÷ charging efficiency”?
In “wall energy = usable capacity × SOC change ÷ charging efficiency,” usable battery capacity and starting state of charge are treated as parts of one vehicle case.