We usually travel out West during the WInter and have spent a January in the Grand Canyon campground. This year we are going to be spending a month or so this Winter in Maryland. In the past we have used a 120 volt portable AC/heat pump to keep the coach comfortable. When plugged in to my Son's house, we only have 30 amp service and this portable heat pump works great to keep the coach warm and it draws only 10 amps. We also have roof top AC/heat pumps but they will stop working at around 32 degrees. The inside portable unit keeps working no matter how low the outside temp drops.
I do not hook up to water unless it is to fill my water tank. I use a 100 watt light bulb in the wet compartment to keep the pipes/pump from freezing. I only drain my black and grey tanks when they are full and have never had any problem with them freezing.
Considering that you have basement compartments under your floor, I am not sure that hay bales would help. They may be OK to keep snow from blowing underneath, or maybe on a modular home, but I don't think they would help a Class A. Maybe a few throw rugs might help.
