Thermostat 101 

During Winter, why does lowering your thermostat during certain times of the day save you money?

When my oldest daughter was at University, she shared a home with 4 other students. They're seeing first hand that heat ain't cheap! She called me for some insight on a discussion she was having with her roommates on how they could save money on their heating bills.  She was trying to convince them that when they left the house, they needed to lower the thermostat from 20°C to 18°C. Her roommates’ contention was that by lowering the thermostat when they are away, the heating system will use more energy to get back up to 20°C when they turn it back on. Therefore, they just want to leave the system at 20°C all the time.
A common misconception associated with thermostats is that a furnace works harder than normal to warm the space back to a comfortable temperature after the thermostat has been set back, resulting in little or no savings. This misconception has been dispelled by years of research and numerous studies. The fuel required to reheat a building to a comfortable temperature is roughly equal to the fuel saved as the building drops to the lower temperature. You save fuel between the time that the temperature stabilizes at the lower level and the next time heat is needed. So, the longer your house remains at the lower temperature, the more energy you save.

Still don’t believe it?  

Think of it this way:  Instead of being gone just a few hours, you decide you are tired of the cold and go to Florida for the rest of the winter.  Do you honestly think you would be saving more energy by leaving your thermostat at 20ºC as opposed to lowering it for the the amount of time you are sipping Mai Tai’s and getting sun burned on the beach? To re-iterate the above statement: “… the longer your house remains at the lower temperature, the more energy you save.”  It doesn’t matter if this time period is a few hours, days, or years!

These facts don’t change depending on if you live in a moderate, hot, or extremely cold climate.  As long as your location follows the Laws of Thermodynamics (which unless you are in some other Universe, it does) this applies to you!