Is the issue of saving propane based upon the length of time you are dry camping and you have concerns about running out, or is it just a cost idea? The batteries should easily be able to cover for one night, then run the generator the next day or use solar to recharge.
In newer Airstream TT, there are some items such as televisions, subwoofer, and possibly others which use electricity even when turned off. When dry camping make certain you do not have anything plugged in to the inverter circuit that you are not actively using.
Ms Tommie Lauer
2015 Serenity 30 RB / 2008 Dodge Cummins 4 X 4
WBCCI #4165 AIR #31871
Happy trails and Good Luck
Ms Tommie Fantine Lauer, Greensboro, NC
AIR #31871 WBCCI #4165 K4MTL