Bright app kWh for gas differ from local MQTT received values in Home Assistant

I've noticed that gas kWh reported by the Bright app are always very slightly greater than the local MQTT values received by Home Assistant. The numbers differ by roughly 2%.

I don't think this is a timing issue. I've just checked the total gas kWh for yesterday, as an example. Bright reports 10.8755 kWh. Home Assistant reports 10.66 kWh.

Can anyone suggest why this might be happening? I'm a novice in all this. Does Bright receive kWh from the smart meter, or is it converting to kWh from cu.m.? Might any conversion be the root cause of the differences?


  • edited August 2023

    Looks like there's a correction factor for temperature and pressure of around 1.02 , which presumably agrees with your 2% discrepancy

    From my bill...

    Units Consumed (Cubic Metres)

    × Volume Correction (for temperature & pressure)

    x Calorific Value (energy in each m³ of gas)

    x 3.6 (convert from joules)

    >> Usage (in kWh)

    For you:

    0.3m³ x 1.02264 x 39.4 x 3.6 = 3.7kWh

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