Changing your air filter routinely will achieve two goals: First, it will help increase the efficiency of your unit. Second, it will keep the air you and your family breathe cleaner.

A clogged filter will reduce efficiency. By not allowing the furnace to release the heat that was in the heat exchange, the unit will short cycle. Short cycling of the unit is very inefficient. On warmer days you may not know or suspect a clogged filter because the house will still feel warm since the furnace is kee[ing up. But on a colder day, or in the cool of the evening, the furnace needs to run longer to keep up with the outsideload on the house. If the filter is clogged, all the furnace can do is turn off and on repeatedly. The reason for this is the overheating of the furnace causing the safety circuit to turn the furnace off. The furnace must cool down before it can turn back on.

If you chose a filter that is more aggressive at removing particles from the air you breath, you have to check it and replace it more frequently as it will clog more frequently. I know what you are wondering  - how long should a filter last? The best person to answer that is you! How often do you dust your home and stir up dust? Do you have wood floors or carpet? Do you have a lot of traffic in your home? These are the top factors that will stir up dust. While the furnace is running, the filter is trapping this dust and other particles. The filter is slowly filling up. So checking the filter more often, rather than less often, never hurts.