Should a thermostat be set to “auto” or “on”?

Although the “auto” setting is the most used setting, the fan will only operate when the temperature requires it.  There are advantages, however, to using the “on” setting.  In this setting, indoor air is constantly filtered through your unit’s air filter, resulting in cleaner air and a more comfortable home.  Many of today’s “modern” furnaces have a motor designed to do this at the operational equivalent cost of a 75 watt light bulb.  There are also after market motors available through your local heating and cooling contractor that will provide the same benefits.