Is It Best To Leave The Thermostat At One Temperature In Winter?

When the season changes, we're often confronted with similar questions — Should we maintain the thermostat at a constant temperature? If so, what is the ideal temperature, and if not, what should you do to reduce your energy costs at home without sacrificing comfort? After all, heating is expensive and may be the largest expense on your bills. The right call depends on your heating system and home insulation. Generally, for a conventional heating system like a boiler or a furnace, it's not advantageous to stick to one temperature in winter.

In other words, while you're asleep overnight, away for work, or on a vacation, you might be able to save on your electric bill by lowering the thermostat. The one exception is when your dated boiler is incapable of regulating its output. However, if a heat pump warms your home, it's best to take a "set it and forget it" approach after you've found the most comfortable temperature setting. It's also ideal to leave the thermostat at one temperature if your home has radiant flooring. 

Some people share misgivings about lowering the temperature for short periods, assuming the heating system will have to overstrain to restore the desired temperature. And the added strain might offset any cost savings from the setback period. However, that's not how this works. Heating works on a differential. The lower the difference between the indoor and outdoor temperatures, the slower the rate of heat loss. This holds especially in well-insulated homes that can retain the existing warmth for much longer. Put simply, setting back the temperature when you aren't around can lead to energy savings, and your heating system won't have to work as hard to restore the lost heat.

In fact, the U.S. Department of Energy estimates that you can save an additional 10% on energy costs annually by dialing down 7 to 10 degrees Fahrenheit over an eight-hour period. When writing for Iowa State University, Human Sciences Specialist Carol Ehlers stated, "Even one degree lower can make a difference. Industry figures for every degree you turn down your thermostat, and leave it for eight hours, you save between 1% and 3% of your heating bill."

But know that keeping your home too cold in the winter could cause serious issues. Temperatures below 63 degrees Fahrenheit may cause humidity issues and result in moisture buildup. You also risk freezing your pipes. It's also highly ill-advised for older adults, who may develop hypothermia if they spend time in rooms cooler than 70 degrees Fahrenheit. So, choose the setback temperature wisely.

Unlike traditional furnaces, heat pumps have slower recovery times and may actually become inefficient if you tinker with their temperature settings. They usually come armed with a supplementary heating system, which kicks on when the main pump must play catch-up (you might find that when the display shows 'AUX'). In such cases, you might end up paying extra or not saving at all. However, if you wish to power down at night, considering cooler temperatures help with sleeping better, check the system's settings. Usually, auxiliary heating comes on when the setback temperature is more than 3 degrees Fahrenheit lower.

The case is a little different if your heat pump is adaptive; that is, it can anticipate temperature differentials, triggering the main pump to start working harder in time for your arrival without bringing on supplementary heating. Setting back the temperature for short stints may be helpful here. But be sure to check your electricity rates. If your utility company has time-of-day rates and the system amps up early during peak hours, you might not save much. Heat pumps with variable speeds and programmable thermostats may also wear down less with setbacks, offering efficiency gains.

You must also maintain a steady temperature with radiant heating. Since they use building mass, they don't recover quickly if set lower, making for an uncomfortable sitting. Plus, the energy savings aren't substantial. As for optimal winter temperature, aim for 68 degrees Fahrenheit (70 for seniors) and work down from there.