Rising energy costs have people questioning whether thermostat setbacks actually save money.

“In most cases, they are cost-effective,” says Carl Pedersen, North Dakota State University Extension Service energy educator. “But there are a few exceptions.”

A thermostat setback occurs when the homeowner turns down the heat for certain periods of time to save money on heating costs. Generally, people turn the heat down at night, when they are sleeping, or during the day when they plan to be gone for several hours.

Residents can turn the temperature down automatically with a programmable thermostat or manually.

People may not use thermostat setbacks as a cost-saving method because of some misconceptions, according to Pedersen. For example, many people believe setbacks are not cost-effective because the heating system has to work harder to heat the house back up to a comfortable temperature.

“This is simply not the case,” Pedersen says. “When the temperature falls below a set level, the system turns on to bring the temperature back above the set level. Once the temperature reaches the set level, it turns off. It is not like the throttle on your favorite automobile, where the harder you push, the harder the motor works. Heating systems are simply on or off.”

Many people also believe that the furnace runs so long to heat the house back up that this offsets any savings. Pedersen says the fuel used to reheat the house is roughly equal to the fuel savings while the home’s temperature was dropping to the setback level. The savings occur while the heating system is at the lower temperature.

“The longer the thermostat is at the lower temperature, the greater the cost savings,” he adds.

According to the U.S. Department of Energy Web site http://www.eere.energy.gov, you can save about 5 percent to 15 percent per year on your heating bill by turning your thermostat back 10 to15 degrees for eight hours. That’s a savings of as much as 1 percent for each degree if the setback period is eight hours long. If your normal heating costs are $1,500 per year, that is a savings of $75 to $225 every year.

To estimate if a setback will save money, you can run a simple test. To start, you need to record the amount of time your heating system runs in one hour at the home’s normal temperature. Next, turn the thermostat down to a desired setback temperature. Give the house time to equalize at the lower temperature and then determine the amount of time the system is running at this setback temperature.

If the heating system runs for 20 minutes an hour at the higher setting and 14 minutes an hour at the lower setting, you will be saving 10 percent on your heating bill each hour the temperature is at the lower setting, To calculate the savings, subtract the minutes the heating system runs at the lower setting from the minutes the system is on at the higher setting (20 minus 14) and divide by 60.

Energy experts do not recommend thermostat setbacks for houses that are running heat pumps. Setting back the thermostat on these systems causes the heat pump to run inefficiently, canceling out any benefits, Pedersen says.

Setbacks also are more difficult for houses with in-floor or steam heating. The difficulty with these systems is their slow response times. Reaching the desired temperature levels with these systems may take a number of hours.

Some manufacturers are beginning to offer systems that track the heat so you can better determine when to set back the temperature. Setbacks are possible with these systems, but determining the proper timing will take some effort by the homeowners, Pedersen says.

If you have any questions on this or any other energy-related topic, contact Pedersen at (701) 231-5833 or carl.pedersen@ndsu.edu.

NDSU Agriculture Communication