Thermostat Myths

Your home’s thermostat turns your heating or cooling systems on and off, controlling how long these systems operate. The longer the heating and cooling systems operate the more energy you use and the more money you spend. You can save energy and money by learning how your thermostat operates.
One common myth is that the higher you set your thermostat when you return home, the faster your furnace will heat up your house. This isn’t true, since most furnaces deliver heat at the same rate no matter how high the thermostat is set. So just set your thermostat at the temperature you’d like, and your furnace will heat your home as fast as it can.
Another myth regards the efficiency of setting your thermostat down when you don’t need heating or cooling, such as at night or when no one is home. This myth states that a furnace works harder than normal to heat your home back to a comfortable temperature after the thermostat has been set back, resulting in little or no savings. This is not true, as has been proven by years of research and field observations. The longer your house stays at a reduced temperature when heating–or at an increased temperature when cooling–the more energy and money you’ll save.
This is because your heating or cooling cost depends mostly on the temperature difference between indoors and outdoors. When you adjust your thermostat down in the winter–or up in the summer–you simply reduce this temperature difference. If you set your temperature back 10 to 15 degrees for 8 hours while you’re asleep or at work, your energy savings can be 5% to 15% on your energy bill.
By the way, you can install a setback thermostat that automatically adjusts your home’s temperature at pre-set times. But you can achieve the same savings if you faithfully remember to change your thermostat whenever you leave home or go to bed.
See The Homeowners Handbook to Energy Efficiency or Residential Energy: Cost Savings and Comfort for Existing Buildings Chapter 6 for more information. For professional information about heating systems and energy efficiency seeSaturn Hydronic Systems Field Guide.