We usually only camp in the milder places in the late season and maybe sometimes it migh get down in the high 20's...
We have a couple of the 1500WATT OIL FILLED portable heatres in our setup... I was worried about the open flame or accessible red hot cores type portable heaters might be a safety issue...
We always run a separate extension cord out to the campground pedestal and plug into their 20AMP service to run our portable heaters... This does not draw from our 30A side of the campground pedestal...
If we need to move some air around the trailer we sit one of those O2-COOL 10-inch 120V/12VDC/D CELL fans behind it. Perfect fit sitting behind the oil-filled heaters and will move some air around the trailer room...
Using the on-board furnace is the back-up heater for us... The 12VDC BLOWER that is on ours is really loud and eats up a bunch of Battery current when we are camping off the power grid...
When camping off the power grid Momabear likes to use one of those 12VDC heated lap blankets while watching HDTV from the local towns... This also makes for heated blanket on the bed as well that doesn't draw alot of DC Current.
Roy Ken