You should replace the filter in your air conditioner approximately every 90 days, if you don't have allergies. However, AC professionals generally recommend changing it every 45 days for maximum efficiency. It is important to use the correct size and type of air filter when replacing it. If your air conditioner is working properly, you can remove the filter and buy one that is identical to it.
Most air filter manufacturers and HVAC companies suggest changing the filter every 90 days or 3 months. This may vary depending on the location of your home, if you have pets, and the age of your system and equipment. If you have pets in the house, you should consider changing the filter every 60 days or 2 months. For households with multiple pets or people with allergies or respiratory conditions, it is recommended to change the filter every 20-45 days.
Vacation homes or vacant homes that don't have much use can expect to change filters every 9-12 months. The more you use your home, the more often you need to change the air filter. The only way to determine how often you need to change your air filter is to perform a visual inspection of the filter each month. After a few months, you will get an idea of how quickly it gets dirty. You may need to re-evaluate if you have a new pet or if the outdoor air quality has been poor. A general rule of thumb for pleated air filters (such as those manufactured by FilterBuy) is to replace the filter every 90 days.
As the filter traps more dirt, dust and allergens from the air, its efficiency decreases. There are several factors that can influence how often you should replace the filter. The most important factor is how often your system runs. The filter collects dust and debris only when the system is operating. The more it works, the faster the filter picks up dirt.
During a cold winter, a furnace filter will need to be changed more often than during a mild winter. On the other hand, you will need to change the filter more frequently during a hot and humid summer than during a mild summer. Pet hair can also clog up filters quickly. Hair fibers from dogs, cats, rabbits and other mammals are larger than dust and dirt particles that normally trap in filters. That means they block airflow quickly. The more important clean air is, the more often the filter needs to be changed or cleaned.
A coarse-media filter, MERV 11 or higher, or an electronic air filter is best for households with someone who has asthma, severe allergies, or difficulty breathing for any reason. An air cleaner may also be necessary for your system. Cheap fiberglass filters require less frequent replacement than pleated filters. Coarse-media filters trap more and smaller dust particles, so they clog up faster than slim fiberglass filters which don't trap as much dirt and debris. Some of these filters can be cleaned with a nylon brush and placed back in the oven or air controller instead of replacing them.
Cleaning should be done outside or in a garage to keep dust and dirt out of your home. If cleaning with a brush instead of replacing the media filter, be sure to change the filter after two or three cleanings as it will not remove enough deeply embedded dirt and debris. In larger homes, more air flows through the filter than in smaller houses so it will get dirty more quickly. Continuous fan mode is another factor that affects how often you need to change your air filter. This setting works all the time until you turn it off and helps balance temperatures in your home as well as draw cool air from basements to help cool upstairs floors. However, running the fan requires electricity so you'll see an increase in your electricity bill as well as bring warm air from inside walls or attic which causes your air conditioner to work longer than necessary. In summary, we recommend changing your air filter every 90 days unless you have pets or allergies in which case it should be changed every 60 days or 2 months.
For households with multiple pets or people with allergies or respiratory conditions, we suggest changing the filter every 20-45 days. Vacation homes or vacant homes that don't have much use can expect to change filters every 9-12 months.