Dear Ida B. Green,
I've heard that turning your thermostat down at night actually makes your furnace work harder to heat up the cold house each morning. How does that save energy?
It's true that you may notice your furnace working longer in the morning to bring temperatures up to daytime levels but it's also true that the furnace worked so much less during the night that you save energy overall. The U.S. Department of Energy estimates that you'll save 10 percent for a 10-degree nighttime set-back.
Your house's actual savings from an eight-hour set-back can vary depending on the temperature outside (the colder it is, the more you save), the energy efficiency of your home (the leakier your house is, the more you save), and numerous mechanical variables.
The Canadian Centre for Housing Technology (CCHT) did a "twin house study" that took some of the variables out by studying identical houses, identical gas furnaces, right next door to each other in the Ottawa area. They found that in these highly efficient houses and cold climate, a set-back of 10 degrees for eight hours at night provided a 13 percent seasonal savings in gas consumption.
So, if you have thermostat-controlled central heating, installing and using an Energy Star programmable thermostat ($50-$100) can pay for itself in energy savings in less than one heating season without sacrificing any of your own personal comfort.
Easy to be Green,