On Sunny Portal installations with two or more inverters, Sunny Portal compares the production of the inverters with each other. If large differences arise between the production levels of the inverters, Sunny Portal may send an error message with the text ‘performance deviation’. The message also states how many percent the inverter in question deviates from the others, or from the average if more than two inverters are present.

By default, Sunny Portal is set to send this error message only if the deviation is 20% or more, in order to prevent messages being sent for normal variations. This setting can be changed; for example, if two inverters are connected to systems with completely different roof orientations and tilt angles. If you have one inverter with panels on the east-facing roof, and another with panels on the west-facing roof, the output of the inverters can easily deviate by more than 20%. For instance, if it’s sunny in the morning (east roof produces a lot) and rainy in the afternoon (west roof lags behind), that might trigger a warning.

To change the 20% setting, click ‘Configuration’ in Sunny Portal and then ‘Device Overview’. For each inverter, click on ‘Properties’.

Then scroll down to where you see ‘Inverter Comparison’ and click on ‘Edit’:

Here, you can adjust the 20% threshold value:

The deviation is calculated based on the specific yield, in kWh/kWp. This makes it possible to compare inverters of different capacities. For a correct comparison, it is important that the accurate amount of peak power (in kWp) connected to the inverter is entered.