I'm not real sure what type of equipement the op has or is asking about.... his description seemed too cover both?
Many of the responders. Seem to be losting about their particular rigs as gospel...
Mine (a 2008 monaco) has:
An energy management system, with butttons for 50, 30, 20, and 15 amps. It automatically sets 50 or 30, and I can manually set 20 or 15. This device controls load shedding, how much the rv will take from shore power.
I also have a panel for the magnum inverter/charger. This thing has. A 100 amp charger, and can use a significant amount of the available shore power. In it's ,menu swettings, I can tell it "what shore power" I have, and that will change it's max charge current, which will affect what the ems system will let me run.
On a 20 amp shore power hookup, I cannot run an a/c unless I also select a lower settiing on the magnum's panel.
And yes, when I do that, the charger uses less electricity.