Some arguments against temperature setforward point to the amount of additional energy required to cool a building back to the proper comfort level after the setforward period. However, most industry sources agree with the energy savings of temperature setforward.
According to the EERE Consumer's Guide to Thermostats and Control Systems, it is a common misconception associated with thermostats that an air conditioner works harder than normal to cool the space back to a comfortable temperature after the thermostat has been set forward, resulting in little or no savings. This misconception has been dispelled by years of research and numerous studies. The energy required to recool a building to a comfortable temperature is roughly equal to the energy saved as the building rises to the higher temperature. You save energy between the time that the temperature stabilizes at the higher level and the next time cool air is needed. So, the longer your building remains at the higher temperature, the more energy you save.
Temperature setforward is a well-known means for saving cooling energy by allowing the temperature in a conditioned space to rise to a specified setpoint when the space is not occupied. The general rule of thumb is that energy savings are typically 1% of space cooling energy use per degree of temperature setforward per eight-hour period. Of course, a number of factors contribute to the cooling energy required for any facility, including building insulation, ventilation, infiltration, windows, weather conditions, and indoor conditions. The above number applies to the time that the temperature is set forward, so if the temperature is set forward for only half the day (12 hours during the evening and early morning), the net savings would be 1.5% of space cooling energy use per degree of temperature setforward.
Fuel and money will be saved after the building reaches the higher temperature. When the setforward period is over and the cooling equipment begins the cooling period, the equipment will have to run slightly longer to restore the space to the occupied setpoint temperature, but it will have been off more during the setforward period, resulting in less overall energy use.
Typical setforward temperatures are in the range of 74°F to 78°F. This is really an individual choice and depends on how comfortable you want the space to be. It is not recommended that the temperature setforward be so high as to open up the possibility of humidity levels that could cause mold or mildew problems.
In other words, temperature setforward DOES save energy.
Photo by: tmib_seattle
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