Setting back the thermostat on your central furnace or heat pump during cold-weather months will save energy and money. The key is finding a temperature at which you and your family are comfortable.
However, selecting the proper temperatures throughout the day and night can be a bit confusing. Of course, you need to balance comfort with savings – but you may be surprised at how quickly you’ll adapt to a lower indoor temperature. Eventually, you even might feel a little uncomfortable at the higher indoor temperatures that used to seem normal.
There are other advantages to reducing the thermostat setting during winter too. If your house temperature is lower, it requires less moisture to keep the indoor air at a given relative humidity level. The fact that your furnace or heat pump runs less often at a lower temperature also means the equipment will last longer and need fewer repairs.
There is not a best furnace or heat pump thermostat setting for all homes and weather conditions. The lower you set the thermostat, the greater the overall savings you’ll achieve. The amount of savings per degree for each nighttime 8-hour setback period ranges from 1 percent to 3 percent. If you’re gone during the daytime, you can set the temperature lower for a total of about 16 hours per day. Unless there are health problems in your family, 62 degrees should be comfortable if you’re wearing long sleeves or a sweater.
Let comfort dictate how low you initially set the thermostat. As you get used to the lower temperature, you’ll be able to gradually lower it more. Be sure to watch for excessive window condensation, which can limit how low you set the indoor temperature; to go as low as you’d like to, you may have to reduce the indoor humidity level.
A common myth is that it takes as much or more energy to reheat a house each morning compared to what was saved during the temperature setback period overnight. The amount of heat a house loses through its floors, walls and ceilings is directly proportional to the difference between the indoor and the 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 home. As a result, your heating system needs to use less power to create the heat toreplace what’s been lost. The amount of heat used to reheat the house, therefore, is less than the amount saved over the temperature setback period.
The only time a temperature setback may not be wise is if you have an older heat pump with backup electric resistance heat and an old thermostat. When it’s time to reheat the house and you set the thermostat higher again, the expensive backup electric resistance heater may come on. For a long, 8-hour setback, you
likely will save – but you won’t see a noticeable savings for just a short 1- or 2-hour setback.