The simple thermostats are easily changed out with a house unit, since the simple ones merely complete a circuit to fire the furnace. I, too, have done this, using a thermostat with its own battery. The bonus for me was that the house thermostat not only reports/controls with actual temperatures, it also allows for setting temperatures as low as 40°F, which is perfect for minimal propane usage while unoccupied. Installation was a breeze, couple screws in the wall and connect the two wires to the appropriate terminals.