With respect to #219, see comment #219 (comment)

The integration use "signed_meter_value_kwh" as source which is not a state variable. Instead there is "signed_meter_value", but this is encoded using Open Charge Metring Format (OCMF) which is described here: https://github.com/SAFE-eV/OCMF-Open-Charge-Metering-Format/blob/master/OCMF-en.md

Looks like this

{
  "FV": "1.0",
  "GI": "ZAPTEC GO",
  "GS": "ZAPxxxxxx",
  "GV": "2.4.2.4",
  "PG": "F1",
  "RD": [
    {
      "TM": "2025-07-22T20:00:00,000+00:00 R",
      "RV": 6211.03,
      "RI": "1-0:1.8.0",
      "RU": "kWh",
      "RT": "AC",
      "ST": "G"
    }
  ]
}

What's useful about this is that this is pushed regularly via the service bus, so it helps keeping the data in HA up to date.