How Often Should One Replace an Air Conditioner Filter?

Systems that are used to filter air and water inevitably reach a point at which they become saturated with filtered materials and need replacement. Whether a drinking water filter or an air conditioning filter, a dirty filter diminishes efficiency and often will make the filtered result more contaminated than the unfiltered materials. Therefore, keep track of how long the filter has been in place so you will know when it is time to replace it.

Importance of Changing an AC Air Filter

A dirty AC filter decreases the effectiveness of the air conditioner by blocking airflow and carrying dirt and other materials through the AC system. The United States Department of Energy estimated that replacing a dirty AC filter with a clean one will improve the efficiency of the AC system by 5 to 15 percent.


In general, the Department of Energy recommends changing your AC filter once every month or two during the cool season. Warm seasons require more frequent replacement, particularly if you use the AC frequently. Filter replacement frequency also depends on what type of filter you purchased. Some AC filters are designed to be cleaned and reused. Replaceable filters have recommended guidelines for how often to change them.

As Needed

Change AC filters more often in the summer than in the cooler months. If your system has a lot of excess dust in it or if you have an indoor pet that sheds hair, the filters saturated more quickly and need replacement more often. Simply check your filters and replace them as needed, even if more than once per month.

Other Considerations

On most air conditioning systems, the filters are located along the return duct. In residences with more than one room, a filter may be mounted to a grate on a wall or ceiling in every room that receives air conditioning. If replacing a filter every month seems cost-prohibitive, change the filter at a minimum of once every three months. However, the money saved on buying air filters less frequently may come back in the form of maintenance and repair costs of an AC system that is clogged with dust and dirt.

About the Author

Eoghan McCloskey is a technical support representative and part-time musician who holds Bachelor of Arts degrees in English and political science from Texas State University. While at Texas State, McCloskey worked as a writing tutor at the Texas State Writing Center, proofreading and editing everything from freshman book reports to graduate theses.