Won't try it out till January, but we now have a 120vac blanket, run from a 1000 watt pure sine wave inverter for the times we don't have hookups. When there are no hookups we'll run it for something like an hour before we get into bed.
In the past we've run the heat and used a heavy down comforter. It was freezing in the bed when we'd get in, must have easily taken an hour for the feet to warmup enough to fall asleep. The memory foam topper is/was like climbing onto partially frozen wood. Fat chance of my wife letting me sneak my cold hands or feet over to get them warm. Hopefully that's a thing of the past.
The wattage of each side of the queen is marked as 160 watts, kind of deceiving though as the power pulses to it, it's not a steady 160 watt draw.