The heaters are only about 150 watts, basically as much heat as a good sized light bulb. They are NOT like electric blankets. I found this out the hard way. First time I tried them, I kept putting my hand under the covers, expecting it to be warm like an electric blanket. The plug is very hard to get into the fitting on the mattress, so I thought it wasn't getting in far enough to make an electrical connection, so I "filed" down the outside of the plug, hoping I could get it in better. (Didn't help, but it made it look ugly.) Ended up giving up and getting into bed, and discovering an hour or two later (the wife had turned it on, even though I had given up) that it was quite warm in there! Then I read here that it's only about 150 watts.
1988 Coleman Sequoia - popup (1987-2007)
2012 Roo19 - hybid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10