What Does An AC Filter Do?

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Updated May 17, 2023

A clean and working air filter is vital to keep your ac effective and functioning. The best air conditioner can’t produce good indoor air quality with a dirty air filter. Whether you have a central, portable, or window AC unit, the air filter contributes to your unit’s overall power, cooling effect, and air quality. These filters — often made from fiberglass, cloth, or paper material — are the main barrier between your air and harmful debris.


  • Air filters are made of fiberglass or cloth material that strains out allergens, debris, and harmful substances from the incoming air.
  • Living with a dirty air filter increases your energy consumption while bringing down AC efficiency and cooling power.
  • Having a clean filter decreases the risk of harboring mold spores or airborne particles that can be dangerous to your health.

The Role of an Air Conditioner Filter

Today, we will dive into what do air conditioner filters do and what you should know about them. We also have a great resource covering what aircon symbols mean, like when it is time to know how to clean an AC filter.

Insider Tip

Ignoring a clogged air filter for even a week can lead to higher energy bills.

They come standard on all types of air conditioners and are used to protect and enhance your air quality. Therefore, understanding and knowing what to do with your air filter is crucial. Below, we’ll explain some of the essential elements of AC care.

But, for more A/C know-how, you’ll want to read how to stop an AC from leaking water, how to winterize an air conditioner, and understand what E1 means on an air conditioner.

It’s also important to know that the type of filter is different between central air conditioners and window/portable units. Central ACs have disposable filters that come with MERV ratings. These have varying levels of filtration, which can be necessary depending on the area you live. With window and portable units, they come with a reusable filter that needs to be cleaned regularly.

And for those with central AC units, we have an article that explains what causes freon leaks in an air conditioner.

Know The Right Filter for Your Unit

Cleaning your filter boosts airflow and energy efficiency. With window/portable units, you’ll either have a vacuumable or washable filter. With these filters, check around every month to see if it needs to be cleaned.

Picking an HVAC filter will depend on your needs and the surrounding air quality. Central AC units have various selections of filters with different MERV ratings. Here, you can go with a standard or pleated filter.

Pleated filters are designed to be high-efficiency filters. They filter out more particles than average without hindering the airflow. Standard filters have varying levels of filtration and are often cheaper. So while many options are available, they likely won’t be as good as the best-pleated filters.

STAT: The different MERV ratings in air filters require them to be changed over different periods: MERV 1-4 should be changed every 2-3 months; MERV 5-8 should be changed every 1-2 months; you should change MERV 8+ every month. (source)


What MERV rating air filter should I use?

Finding the right air conditioner filter depends on your budget and the overall level of air quality you want. For example, MERV 1-4 will be cheaper but won’t catch everything, while an air filter with an 8+ high-quality MERV rating will prevent smaller particle sizes from entering the duct system.

What is the meaning of a MERV rating?

It stands for “Minimum Efficiency Reporting Value.” The different ratings measure the particle sizes that the filter can keep out.

Where is the HVAC filter located?

The filter is found next to the indoor unit. The filter will be in a slot that can be removed and replaced easily.

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