On my 2014 FC 20' there are heating pads. I did a complete check of the amp draw of each 12 volt
part, but was not able to measure the heat pad draw as apparently they have a thermostat on them, and if turned on in warmer temps they do not heat and use power. So, until I can measure it in cold weather when home (I am at my winter home now, and no AS, sniff) I can't tell you what their draw is.
On the smaller AS, they use a direct vent furnace now, the heat comes out the front of the furnace only and there is no ductwork at all. I assume that is the reason they use the heating pads vs the little heat duct to the tanks. I have never been impressed with the heat duct system for the tanks anyway. Not only does it not deliver much heat but especially the way AS has installed them, the holes through the floor often become a mouse highway between the underbelly and the main cabin. And unless the ends of the 2" ducts have screening on them, the meeses can run right up the tube and into the furnace ducts and probably get out somewhere. I hate meeses and mice, you might note.
The heat pads on my FC only heat the tanks, and there is a good bit of exposed piping outside subject to freeze issues. Why heat the tanks and leave the drain pipes and valves exposed? Does anyone at Airstream consider these things at all, ever? Does anyone who designs them actually ever camp in them? Airstream desperately needs a real world feedback loop which they listen to.