Question: what is the best temperature to leave an empty house?
Answer: You should set the temperature around 50 to 60 degrees Fahrenheit (℉). Most of the time, dropping the thermostat to 50 °F to save some heating bill is fine. You don't need to set your thermostat too high if your plumbing runs within the interior walls. You should have no issues by leaving the thermostat at 50 °F.