Will you have access to 110v power? It’s wonderful to have a backup, safe electric heat source. In late November, on a hunting trip in northern Minnesota, I stayed in a mid-80s pickup camper for two weeks. I used one of those little, oil-filled electric radiators because I had access to electricity. It has two settings: 750 watts and 1500 watts. If I tried to use the coffee pot, the breaker would trip. Once the camper was warmed up, 750w was more than enough to keep the temperature at a comfortable level. There was also a thermostat on the radiator. Here is a guide for camper shells Temperatures in the daytime range from the mid-thirties to the low-forties. Upper twenties at night are the lowest. In most cases, they are in their mid-twenties.