I suppose the answer depends on what model camper you buy, how many people will be in the camper at the same time, and whether you'll cook indoors. Also, whether you cover the bed-ends.
I've never used a thermometer to measure the temperature in my hybrid, but I have always been able to keep it comfortable. I use a fan when necessary, as well as a small electric heater. I do have a propane furnace, but I depend on the electric heater whenever I can. I use the a/c mostly to remove moisture from the inside of the camper. Otherwise, I keep the windows open for good circulation.