Shelly EM 1 weird returned power measured


I have a Shelly EM 1 to measure the power consumption of my airco.
The airco is on a dedicated circuit breaker.
Also I have solar panels that are also on a dedicated circuit breaker.
See picture.

When the solar panels are producing a lot of energy I notice that the Shelly registers returned power around 5 watts. The same measurements are also in the Shelly app visible. So it’s not a Homey app issue.

Can some explain how this is possible?
I know it’s not a dedicated Homey question, but I hope someone can help me.