For your first charging sessions, here are our recommendations, based on tests carried out with the auditing firm Bureau Veritas:
The difference between measurements from an MID-certified charging station and those from Voltaback averages +1.22%. This can go either up or down, so any gaps tend to balance out over the month, giving a similar total by month's end.
This error rate was obtained under a calibration protocol involving:
2 long overnight charging sessions
Battery charge level moving from at least 20% to more than 80%
It's also worth checking your first charging sessions to make sure your home charging location has been properly calibrated.