[twic]

I have an electric blanket. The way it works is that you put it underneath the sheet, on top of the mattress. Moisture getting trapped under it isn't really a concern, because i lie on top of it. From the sheet up, the bed works in the normal way.

I turn it on for 30 - 60 minutes or so before getting into bed, to warm the bed up, and turn it off once i get in. I have tried leaving it on all night on the lowest setting, when it is very cold, but i wake up dehydrated.