How accurate is 3 EM

    I wonder how accurate is shelly really?
    I'm comparing the values I get from electricity company and shelly.

    Import

    1 October: 22.78 kWh (real) 24 (shelly)

    2 October: 30.59 kWh (real) 32.1 (shelly)

    3 October: 25.69 kWh (real) 27.3 (shelly)

    4 October: 30.19 kWh (real) 31.4 (shelly)

    5 October: 37.33 kWh (real) 37.5 (shelly) almost correct...

    And export(returned) is even worse

    1 October: 8.29 kWh (real) 9.51 (shelly)

    2 October: 0.15 kWh (real) 1.6 (shelly)

    3 October: 0.79 kWh (real) 2.3 (shelly)

    4 October: 0.25 kWh (real) 1.4 (shelly)

    5 October: 0 kWh (real) 91.4 (shelly) ??????



    Is the calibration wrong, I thought it should be around 1% difference (99% correct)
    :/

    That's due to the lack of independent counters for import and export. It's been discussed here multiple times. To get better results, you'd have to log the current power in your home automation system and compute the values there, or use another measuring device.