You may not have given it much thought, but if you take a look at your thermostat, you’ll probably see that it has two settings for the fan: auto and on. On the auto setting the fan only runs when the system is either heating or cooling. With the fan set to on, the fan runs continuously.
There are pros and cons of each setting. The choice of whether to set your fan to on or auto depends on your situation. Leaving the fan in the on position uses more electricity than setting it to auto. If you have an older traditional furnace and air conditioner system, the fan uses quite a lot more electricity when it runs constantly. Depending on energy costs in your area, continuously running the fan on these systems could cost $300 to $400 more than leaving the fan on auto.
If you have a new, energy efficient HVAC system with a variable speed fan, the cost difference is somewhat less; about $50 to $100. In addition, running the fan continuously will reduce the system’s ability to dehumidify the air in your home. Some of the moisture that condenses on the coils and would ordinarily drip into the drip pan and be drained will instead be blown back into your home.
The advantages of running the fan all the time include improved indoor air quality and more even heating and cooling. By continuously circulating the air, hot and cold spots in your home will be less of a problem. Also, your furnace filter will capture more dust and other airborne contaminates if the fan is always on.
