I have noticed that when we are running from just the grid or just the battery that the power used is always about 50W more than the load reported on the web app. If the readings are accurate then that is far less efficient that the 97% stated when the load is only about 300W.
When looking on the phone app is seems to inflate the load to match the incoming power, so it looks much better.
The value in the app is because you have the 'show calculated load' setting turned on, so the inverter losses are shown as being part of house load.
In the portal, the value difference is due to the losses and I believe is broadly accurate (all caveats of snapshots vs true realtime apply), so yes, the efficiency at low loads is worse than higher loads. My Gen 2 seems to be about 93% efficient running at over 2kW output but will drop into the 70s when covering baseload of 1-200W.
Yes I noticed that setting today and turned it off.
When running from the grid only it isn't doing anything at all apart from monitoring but it takes 50W, which seems a lot just to be in standby. It is more than the desktop PC I am typing this on. Seems poor for an embedded system.
Fortunately it is mounted in an integral garage that I use as workshop, so at least the heat is welcome most of the year.