ledger
/ˈlɛdʒə/ noun- A book in which accounts are recorded.
- A record that cannot be argued with afterwards.
8 January 2026 · Amsterdam · 1 minute
Every charging session ends with a ledger entry: who charged, where, how much, at what price. Between a car, a charger, an operator and a card provider, that single line passes through four systems, each with its own idea of what happened.
1
One session, four records
Table 1
Table 1. The same session, as four parties recorded it.
Table 1. The same session, as four parties recorded it.
| Party | Energy | Duration | Price |
|---|---|---|---|
| Car | 31.8 kWh | 47 min | – |
| Charger | 32.4 kWh | 49 min | – |
| Operator | 32.4 kWh | 49 min | €17.50 |
| Card issuer | – | – | €17.50 |
The car measures what went into the battery; the charger measures what left the cable. The difference is heat, and it is real.
2
Settling
python
# A session is settled when the parties that measure energy agree within tolerance.
def settled(car_kwh: float, charger_kwh: float, tolerance: float = 0.03) -> bool:
return abs(charger_kwh - car_kwh) / charger_kwh <= toleranceThree per cent covers losses in charging. Anything more is worth a question, and a ledger is where questions are asked. See tariff.