My dog and I lived in our R-Pod 179, all of November and half of December in 2014 in Illinois at 2 different state parks. We were bird hunting. It got down to -19 below 0 two nights. YES, it was cold out side, but I ran one small space heater on low/med., at times turning it down to low. I only used the furnace "twice" on the -19 nights. We were warm and comfortable the whole time. My dad and grandma drove from Michigan to spend Thanksgiving with me. They couldn't believe how roomy and comfortable the trailer was. They never got cold or too hot.
I never put water in the tanks, used the park bath houses, and bought drinking water. Dishwater I poured in sinks in park bath house.
My current A/C (Under Warranty) died over 4th of July weekend. Dealership is installing a new unit w/heat strip per my request. I'm paying the cost difference between standard unit and upgrade (Forest River agreed to it - WOW). Only reason for the upgrade is: Space heaters take up floor space, they get kicked or tripped over (at night), dog can't lay on floor because they blow heat on him, making him hot and uncomfortable. (When a dogs uncomfortable or miserable - they let their owners know it) Happy dog, Happy camping!

I'll be doing 2-3 weeks this winter hunting in Montana.
I will be adding the underbelly cover - only for protection from road debris and road salt.