Last Friday night (1st night of the trip), the temps were supposed to be in the low 30s. So I plugged in the mattress & turned it on "6" (the highest setting) about an hour before I went to bed. I kept checking under the covers & the bed didn't seem to be getting warm. I stuck my hand between the mattress & the memory foam pad & I did feel heat from the mattress but it didn't seem to be going through the foam pad. I wasn't sure how well it was going to work but left the heat on (and set on 6).
When I first got in bed, I was pretty comfortable except my feet & legs were cold & my nose was really cold. (Thermostat was set on about 60 so the bunk end was cooler than that.) I wasn't sure how well I was going to be able to sleep & wondered if I should find another blanket or something to throw over my feet. After awhile I dozed off. Woke up a little while later and thought, "OMG...I am so WARM!" The heat had made its way through the pad & I was nice and toasty for the rest of the night. Even my nose wasn't cold any more! Heated mattresses ROCK!!
Seemed to keep Molly (my cockapoo) comfortable also. She was curled up against my back (on top of the covers) and barely stirred all night.