I purchased for my husband.   He fusses that the bed is cold.  I don't want my side any warmer.  It says do not cover while turned on.   So, a couple of hours before he goes to bed, he pulls down the comforter, puts this on top of the sheets and turns it on.  When he gets into bed, he turns it off and pulls up the comforter.   He loves that the bed is warm and once he goes to bed, it does not get cold again.