The Importance Of Changing Your AC Air Filter

Changing your air conditioner's air filter is one of the easiest things you can do to keep it in great shape. Unfortunately, it's also the one thing that many homeowners forget to do, resulting in a wide range of performance and comfort problems. Learn why it is so important to have your AC system's air filter property replaced on a regular basis.

What Happens If You Don't Change Your Air Filter?

A typical air conditioner relies on airflow for many of its operations. Not only does it need proper airflow to carry released heat away from the condenser portion of the unit, but also to circulate cool, comfortable air throughout your home. Unfortunately, the air in your home contains a broad range of airborne pollutants, ranging from dust, pet dander and dead human skin to carpet fibers, pollen, bacteria and various volatile organic compounds (VOCs) from household sprays and man-made materials.

Trapping all of these pollutants before they reach the blower fan and evaporator coil is the air filter's job. Over time, however, dust and debris buildup slowly constrains the amount of air that's able to flow through the filter. Eventually, the filter becomes so thoroughly packed with debris that it's nearly impossible for the AC system to draw air through the return air vent.

As a result, the blower fan has to work harder and use more energy to pull air through the now-clogged air filter, using more energy and generating more heat in the process. This often causes the blower fan motor and other parts of the AC system to wear down and fail prematurely. What little airflow that does come through bypasses the filter, allowing dirty air to circulate through the AC system.  

How Often Should You Change Your Air Filter?

The conventional wisdom among most HVAC technicians is that you should change your AC system's air filter at least once every 3 months. Some technicians recommend monthly air filter replacements to ensure the best performance and air quality from your AC system.

However, this conventional wisdom isn't as ironclad as you'd think. Air filter replacement intervals actually depend on a variety of factors, including the current quality of your home's indoor air and the type of filter you're using. For instance, you may find yourself changing a typical fiberglass air filter more frequently if dust is prevalent in your home. Meanwhile, a home with relatively good air quality won't need frequent air filter changes.

Having multiple pets, an overly dusty indoor environment or heavy outdoor pollution can affect how often you change your air filter.

Which Air Filter Should You Use?

Given the overwhelming number of air filters available, choosing one that suits your AC unit's needs can be a bit difficult. There are several factors to consider as you look for your next air filter replacement:

  • Type – The most common types of air filter on the market are usually made from fiberglass or pleated paper. The latter is the cheapest option, but offers the weakest filtration performance. Pleated paper air filters are usually better at trapping harmful airborne particles, but at a higher purchase price. Some air filters come with a static charge for trapping particles, while others trap odor and VOCs using activated carbon and other sorbents.
  • Rating – Air filters are rated based on their Minimum Efficiency Reporting Value (MERV). Air filters with a relatively low MERV score are generally less effective at filtration than their higher-rated counterparts.
  • Special features – Some air filters are reusable, requiring only a careful rinse and some time to dry before being put back into service. Others (such as the HEPA filter) are designed to trap as many airborne particles as possible.

In most cases, your manufacturer will suggest the best air filter your AC system needs. However, it's up to you to decide if you want to upgrade your air filter replacement to one that offers better filtration performance and longevity.

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