We have the Arctic Pak on our Sunseeker and I don't use it. When it's below freezing we are always using the propane furnace. It heats the tanks, water pump/filter compartment, and sewer connection compartment.
Once we were camping with only a 15 amp hookup when it got to 19 F. We were fully exposed to a 15 mph wind all night. We kept the coach about 70 F. When I checked the compartments the next morning they were about 50 F.
A comment on the reply from FR that the Arctic Paks don't work unless they have 13.5 volts. That's not totally correct. They are simple resistance heaters and the heat output is directly proportional to the voltage they receive. They will put out less heat at 12 volts than 13.5, but will still work.
2011 Sunseeker 3100
1997 Pathfinder Toad