Symptoms
- kWh added shown by the car doesn't match what the charger or app billed
- Cost per session seems higher than expected for the electricity used
- Home electric bill doesn't match the car's reported usage
- Public charging session shows a different total than the receipt
Likely causes
- CommonCharging losses between the wall and the batterySome energy is lost as heat during charging, so the electricity used from the wall is always somewhat more than what the battery actually gains.
- CommonPublic charger billing by time or session fee, not just energySome networks charge per minute or add session/idle fees rather than billing purely by the kWh delivered.
- PossibleHome utility rate structureTime-of-use rates or tiered pricing can make cost calculations look inconsistent with a simple flat per-kWh estimate.
- Less commonApp or car meter calibration differenceMinor differences between how the car and the charger measure energy delivered can create small discrepancies.
What to do
- Check the exact pricing structure of the charging network you used, since some bill by time or add fees rather than purely by energy delivered.
- Compare the car's reported kWh added to the charger's or app's reported kWh delivered, expecting the car's number to be slightly lower due to normal charging losses.
- Review your home electricity plan for time-of-use or tiered pricing that could explain a cost that seems different from a flat rate estimate.
- Keep a log of a few charging sessions with both the car's numbers and the charger's or utility's numbers to spot a consistent pattern.
- Understand that small discrepancies of a few percent between measurements are normal and not a sign of a problem.
- If numbers differ dramatically and consistently, report it to the charging network or utility, since it may be a billing error worth disputing.
When to call a pro
If a public charging network's billing consistently seems wrong beyond normal charging losses, contact that network's customer support to dispute it.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.