Sessions

A session represents a single charging event — from the moment your car starts drawing power until it stops. Every session records how much energy was delivered and, when applicable, how many ERE-credits were earned.

Session object

{
  "id": "c3d4e5f6-a7b8-9012-cdef-123456789012",
  "charger_id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "charger_nickname": "Garage",
  "started_at": "2026-04-08T18:30:00Z",
  "ended_at": "2026-04-09T06:45:00Z",
  "kwh": 42.37,
  "status": "completed",
  "ere_credits": 6.36
}

Fields

Field	Type	Description
`id`	string (UUID)	Unique identifier for the session.
`charger_id`	string (UUID)	ID of the charger this session belongs to.
`charger_nickname`	string	User-defined name of the charger.
`started_at`	string (ISO 8601)	When the session started.
`ended_at`	string (ISO 8601)	When the session ended. `null` for active sessions.
`kwh`	number	Total energy delivered, in kilowatt-hours.
`status`	string	`active`, `charging`, or `completed`.
`ere_credits`	number	ERE-credits earned by this session. `null` if not yet calculated.

Session statuses

Status	Description
`active`	The charger is connected and a session is in progress.
`charging`	The charger is actively delivering power.
`completed`	The session has ended and final energy values are recorded.

Energy calculation

Joulo calculates kwh from the best available data source for each session:

Direct kWh value from the charger (if reported)
Energy in watt-hours, converted to kWh
Difference between meter start and stop readings
Live meter reading minus meter start (for active sessions)

This ensures accurate energy values regardless of which charger brand you use.

ERE-credits

Each completed session may earn ERE-credits (Energie Rendement Eenheden). The ere_credits field shows the number of credits earned. Credits are calculated based on the energy delivered during the session and depend on whether the charger has a MID-certified meter.