The Load terminal will supply switched dc power for the load, I.E. lamp, which can be programmed when you want to the lamp to go on and when to go off, it is also not made to be connected heavy load with high inrush current such as Inverter.
Did you download the user manual?
Look at your user manual: Local load mode
Under caution:
CAUTION: If an inverter is to be connected to the system, connect the inverter directly to the battery, not to the load side of the controller.