My house thermostat is set at 68 as well. We run 66-68. I just set up a 3x2x12" pvc enclosure with a 40 watt VE RHP. It is my first setup with RHP heating. It seems to have no problem maintaining 88 hot side 80 cool side and isn't on constantly. I was concerned I would need a larger one, but it seems to be doing well. It's been running perfect temps for 24 hours. I am giving it another 24, then setting up with substrate and dialing in humidity.