If you are going to use a PVC cage, then skip a CHE and just use a radiant heat panel. If it's a glass tank, then for wattage, I would get a 150 watt and a lamp dimmer from a hardware store. That way you can adjust it to any temp yet still have enough headroom for more heat in the winters if needed. Or better yet, use a T-stat on it but make sure its a dimming or pulse proportional. I use Herpstats personally. I would avoid on/off types like Rancos or Johnson ones for a CHE. They work fine for UTHs though.