I am monitoring a Solis inverter and a Shelly EM with HA. Just added a Local Bytes plug in to the mix as well. The inverter and the EM track each other pretty closely [within 3V] but the Local Bytes plug is reading +10V.
From the way I understand grid-tie inverters to work, my intuition is that the inverter is likely to be the most accurate device here? Inevitably, it looks like they’re not linear, the EM and the inverter diverge by 3V at 0900 and by 0.1V at 1500.
My idea here is to just re-calibrate the Local Bytes plug to the average of the inverter and the EM.
For what it’s worth, I also have a no-name multimeter and kill-a-watt clone to compare with.