I've used exactly 1 seat warmer, so don't know how this relates to other heat pads. But the one I had did not cycle off, it stayed steady at roughly 100 watts for its entire use. That works out to roughly 0.9A @ 12v and roughly 7A for a useage of 8 hours.I've been trying to find out what the energy consumption is on the 12V bed warmers.
My wife wants one and I cant tell her if we can afford it or not, energy wise that is.
I had two of the $95 ElectroWarmth pads fail.As far as the smaller (twin) 12v pads go, this one seems to be the most common from what I can tell. It draws 6.2A.
https://electrowarmth.com/shop?olsPage=products/t36-12v-bunk-warming-pad-non-fitted-36-x-60
Using two of these has been my fall back position, but a queen would be much preferable.