Ask Bob — March 2022

Bob Pierce headshotBob Pierce answers questions about energy efficiency, consumer products, and cooperative governance. He is Clearwater Power’s Chief Operating Officer and welcomes your questions on our Ask Bob page.

Q: Is it better to keep my house warm when I’m gone or let it cool down and warm it back up when I get home?

A: It is more efficient to heat the home when you want it to be warm and to stop heating it when there’s no one there.

In the wintertime, heat will move from your home to the outdoors. It is unavoidable. You can slow down the heat loss with good insulation, good windows, and sealing air penetrations. But, you cannot stop the heat loss. So, it is best if you don’t use energy to heat a space unless there are occupants who need to be warm.

There’s a persistent and long-standing belief that it will take more total energy to heat a cold home. But the math doesn’t support this claim.

It is worth noting that we don’t want homes to get too cold. You’ll want to use some heat to keep pipes from freezing and to keep condensation down. When air is warm, it can hold some moisture. The colder the air gets, the less moisture it can hold. If a home gets cold enough, moisture can collect and cause mild damage to wood surfaces. The lowest setting on a thermostat is usually 55 degrees. A programmable thermostat makes it easy to drop the temperature when you leave the house and warm it up again before you get home.

There is an exception to this rule. If you have a heat pump/electric furnace and if you use a manual thermostat, then it would be better, especially in the coldest months, to keep the house warm throughout the day using the heat pump rather than cranking up the less-efficient electric furnace when you walk in the door. We offer rebates on several models of thermostat. Learn more on our Rebates page.