I was living in Alaska when I had my Casita, so the climate doesn't apply to most Casita owners. I found that when camping at temps below freezing the
furnace cycled on and off very frequently. This will quickly draw down a 12v
battery when
boondocking, so you need a power source. However, it did stay quite comfortable in temps down in the teens. The "heat strip" on the AC unit was not adequate to maintain comfort in those temps. Off course, the plumbing starts to be an issue at that point, too.
After moving to the lower 48, I continue to frequently camp in sub freezing conditions. Such as high mountains of Colorado, and hunting camps in winter closer to home. I ended up getting a
Bigfoot because of the better insulation and protected plumbing. The insulation and the double-pane
windows on the
Bigfoot do maintain interior temps much better. However, most people don't really want to go camping in freezing weather and probably have no reason to spend extra money on a 4-season trailer. The Casita is a great 3-season trailer, but not ideal for true winter camping. I understand that the
Oliver can be purchased with thermal pane
windows and enclosed plumbing, too. Not sure of their insulation value. But there again, that unit costs about double a Casita. I also used in old
Scamp in Alaska. Basically the same insulation as a Casita with the same results.