Since we camp at altitudes too high to use the small propane heaters, our only option is to use the solar to keep the batteries up and use the furnace. It was annoying when it woke me the first trip, kinda reassuring when it did on the second trip and now, it doesn't wake us up at all.
A quieter furnace may be the answer if you are only setting the stat to 55* or so. We have a 3 season trailer and even on below freezing night the furnace only runs a few times when we set the stat low. Now that we have solar we set it at 74* deay and night and never think of it.