What we measure
EEVEE takes the energy that actually passed through the car's charging port (the grid or AC side), not only the energy stored in the battery. Battery-side figures are lower because of losses when AC is converted to DC. Cars often show this separately as "charging efficiency", commonly around 85 to 90% or more, depending on the charging current and the battery's state of charge.
Reimbursement is based on the port measurement, so drivers are paid for the energy they took from the grid.
Why your wallbox and EEVEE can show different numbers
We compare three measurements. Each of them is allowed a small error compared to the home electricity meter:
Charging station ↔ home electricity meter: max. 2% deviation (the usual MID / fiscal meter tolerance).
EEVEE (vehicle port) ↔ home electricity meter: max. 2% deviation.
So charging station ↔ EEVEE: up to 4% difference is possible, even when both are within spec compared to the actual meter.
Why this is compliant in Belgium
The Belgian circular on the reimbursement of home charging (2024/C/77) asks for an objective, verifiable calculation with a maximum deviation of 2% compared to the meter. A MID-certified charging station is not required. Because EEVEE stays within 2% of the meter, the data is compliant.
Measuring through the vehicle has one more advantage: it identifies which car took the energy. A shared wallbox cannot guarantee that.