Standard fiberglass furnace filters should be changed once a month, and 3-inch high-efficiency furnace filters should be changed every three months. Washable furnace filters should be cleaned once a month.
Furnace filters must be changed more regularly in homes that are more prone to filter clogging, such as homes with pets or smokers. A clogged furnace filter requires the furnace motor to work harder and increases the possibility of it blowing out. The filter also improves air quality in the home by removing debris and helping residents with allergies and asthma breathe easier. A clean filter also lowers energy bills by ensuring the furnace is not running as often.