I copied this from a RT 2005 Owners Manual:
Dry camping battery conservation:
While dry camping, (no 110 VAC power available) to conserve battery power, it is recommended to switch the inverter to the off or charge position, if the inverter is left in the ON position, it will continue to draw 1.25 amps.To ease in switching of the inverter,we recommend installation of the optional remote switch and harness, (Part # APSRM4).
My 2004 Owners Manual did not contain this info.
Here's how to make a switch for the Tripp Lite inverter in a Roadtrek: