KDogg~ Mine are the same way. In the big tanks, I have to turn them up to 82* to keep them at 80*. The one on the 20G tall, it set at 79*, and keeps it at 80*. Two of my tanks have plastic coated wire tops, not the regular hoods.
ThinCat~ I keep my tanks around 78*-80*. Sorry, didn't see your question until now lol.