I have the UTH hooked up to a rheostat. The rheostat is pushed up all the way. I'm not sure the wattage of the UTH. It's a Zoo Med UTH for a 10-20 gallon tank.
I have two thermometers with probes - one under cool side hide; one under warm side hide. I have a thermometer/hygrometer placed inside the tank in the center, 1 inch above substrate.