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Thermostats: How Low To Go?

I hear how important it is to lower my thermostat setting during the winter. It seems it would just take more energy to reheat the house each morning. What is the best thermostat setting for the most savings?—Don G.

Selecting the proper temperatures throughout the day and night can be confusing. You want to balance comfort with energy savings. It is surprising how comfortable you can be at a lower indoor temperature during the winter once you become accustomed to it.

It does save energy overall if you lower the temperature setting on your furnace or heat pump thermostat. The actual amount of dollar savings depends primarily on how low you set the thermostat, how long you have it set back, and, to a lesser degree, your climate.

There is not a “best” thermostat setting for all homes. The lower you set it, the greater the overall savings will be. The amount of savings per degree for each nighttime eight-hour setback period ranges from 1 percent to 3 percent.

Because many people are also gone during the day, the temperature can be set lower for about 16 hours a day. Unless there are health problems in your family, 62 degrees may be comfortable if you wear long sleeves or a sweater. However, the general recommendation is to set the thermostat to 68 degrees in the winter, and 78 degrees in the summer.

Reheating in the morning
It is a common myth that it takes as much energy to reheat a house in the morning as was saved during the temperature setback overnight. The amount of heat a house loses through walls, ceilings, and floors is directly proportional to the difference between the indoor and outdoor temperatures. Air leakage into and out of your house also increases with larger temperature differences.

When the indoor temperature is set lower, the indoor-to-outdoor temperature difference is smaller, so less heat is lost from your house. Therefore, your furnace needs to use less energy to replace the lost heat.

The only time a temperature setback may not be wise is if you have a heat pump with backup electric resistance heat and an old thermostat. When it is time to reheat the house and you set the thermostat higher again, the expensive backup electric resistance heater may come on.

To avoid this, install a special setback thermostat designed for heat pumps. These thermostats have circuitry to keep the backup resistance heating elements off after the setback period.

Mail requests and questions to James Dulley, Kentucky Living, 6906 Royalgreen Drive, Cincinnati, OH 45244, or visit

Low humidity aids furnaces
There are other advantages to lowering the thermostat during the winter. If your house temperature is lower, it requires less moisture indoors to keep the air at a given relative humidity level. The fact that your furnace or heat pump runs less at a lower indoor temperature means it will last longer and need fewer repairs.

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