I would say both heating and cooling will also depend on where you measure the temperature in the trailer. The tent-ends will always by cooler/warmer than the middle of the trailer, simply because they're not insulated. You can mitigate that with reflectix and/or pugs and that will make a difference of few +- degrees. That said, we have camped with temps down to 30F and managed quite well. I never crank the furnace to more than 65F as it will introduce too much condensation. Besides, as long as we take the chill out of the air you can sleep comfortably with a good sleeping bag. If it really gets cold we put a heated blanket under the sleeping bag and that makes it even too hot for my liking sometimes!
And yes, I do own a hybrid :)