I have to disagree with Chuck. We ran a 1500 watt heater on a 25 degree night and my furnace never cut on one time set at 60. The furnace will heat you up sure. But the problem is it won't stay off 5 minutes before having to cut back on. The constant heat from a 1500 watt heater works great in my htt. I was shocked how well it did. Turn your furnace on when you arrive at camp. Get the camper warm. Then run the electric heater to maintain your warmth. Save your propane. When you wake in the morning turn the furnace up to 70 to knock off the chill. My best advice for you is buy a small electric heater. Constant heat is the key for htt. Warning though, even though the camper stayed around 60 the beds were around 50. Expect a 10 degree drop.