For us in case of power going out it's a combination of fireplace (that's mainly for the human and for legged critters), generator to keep the essentials running (fridge, freezers, lights and incubator should there still be eggs in it), and finally buddy heater (propane heater that runs clean) which heats the snake room.

Now as a normal daily thing (not emergency) the main snake room (Ball Pythons and Hatchlings) is heated with a oil filled heater and a reliable thermostat. The office/colubrid room stays at room temps.