MQTT Victron Intergration - Find Potential Power in Off-grid System

Hi, I have an off-grid system using the victron mqtt intergration.

Does anyone know a good way of discovering the potential power the system could deliver at the current time once the batteries are full and there is no load?

The requirement is automating a selection of pumps and immersions to run once the batteries are full. The problem is only matching a 3KW immersion when 6KW is potentially available. Of course the flip side of that demanding 6KW when only 3KW is available and running the stored energy down.

All thoughts welcome. Thanks