How Often Should I Change the AC Filter?

The air filter is a vital component of the HVAC unit. If not maintained properly or replaced on time, it can lead to several problems. Continue reading to learn how often to change the AC air filter.

What Does the AC Filter Do?

The AC filter is essential in regulating the indoor temperature of a building and keeping the air free of contaminants. The filter media is designed to trap contaminants in the air, preventing them from damaging the other components of the unit and improving the air quality.

changing the AC filter
Image Credit: Canva.

How Often Does the HVAC Filter Need Replacement?

The frequency of how often you need to replace the filter depends on its type and condition. For example, if you have pets, you may need to change the filter more often. Depending on your usage, you can expect to change the AC filter every three to four months. According to FilterKing, you should have frequent inspections of the air filter to ensure it is in good condition.

Air conditioning filters often come with manufacturer-recommended guidelines on when you should replace them. However, running an HVAC system with a dirty air filter can damage its components and decrease efficiency. In addition, if you have asthma or any other respiratory allergies, you may have to replace the filter more often.

Signs of AC Filter Needs Replacement

Higher Utility Bills

A dirty air filter can restrict the airflow through the cooling and heating system, requiring the AC to work harder. As a result, it consumes more energy – leading to a spike in utility bills. Replacing the air filter can make the HVAC unit more efficient and reduce energy consumption.

Poor Airflow Through Vents

A weak air supply through the vents is another sign that the air filter requires replacement. Airflow is reduced when impurities build up in the air ducts or blower fans. Prolonged obstruction of airflow can lead to permanent damage to the AC components.

Bad Odors Coming From the AC

A musty smell coming from the AC could be caused by mold or mildew growth in the air filter. When mold develops within the HVAC unit, it circulates in the air through inhalable spores, leading to health problems. Another cause of the musty smell could be the pet dander trapped in the air filter.

The AC Makes Strange Noises

Dirty air filters can cause the AC to make strange noises, including clicking, humming, or rattling. If you hear such noises from the unit, you should change the air filter. You can perform an AC inspection to check if the air filter needs replacement.

Inadequate Cooling

If your home feels humid and stuffy despite the air conditioning being on, it may indicate an underlying problem with the air filter. Due to restricted airflow, the cooling power of the AC is reduced.

AC filtering process
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Factors That Impact How Dirty Your HVAC Filter Gets 

The following factor affects how quickly the HVAC air filter requires replacement. The actual frequency of the replacement will depend on your air filtration standards.

Pet Dander

Having pets around your home is also one main reason your AC filter gets clogged up quickly. Dogs and cats tend to shed, especially when they are playing or getting petted. Their dander and hair get airborne and end up in the HVAC air filter. This clogs up the HVAC air filter, and if you do not replace the filter frequently, it will cause the components to break down eventually. You can try brushing your pet every other day to reduce the amount of hair and pet dander in the air.

Air Duct Leak

If any holes in the ducts or pipes carry air indoors, the outdoor dust and debris or contaminants from your attic can make their way into the HVAC system. When dust and debris enter the system, it will stick to the filter, causing the air filter to clog up faster.

Installing the Wrong Filter

Using a filter with a higher MERV rating than the HVAC system requires can cause it to clog up faster. This is because filters with higher MERV ratings have more thickness and surface area that traps even the smallest particles. This results in the filter getting dirty quicker than expected, requiring more frequent replacements.


Typically if the HVAC system operates a few hours every day, its air filters can last longer, but if it keeps running throughout the day, it will cause the filter to clog up faster. This means that people who live in areas with warmer weather may end up replacing their AC filters more often due to frequent usage of the HVAC system.

Air Quality

If you live in an area where the outdoor air has a lot of dust, it will collect in your HVAC air filter and clog it up. The indoor air quality also affects air filters. For example, if a person smokes inside your home, it can cause the air filter to clog up faster. Dusty rooms or objects around the house can also lead to the air filter getting dirty more quickly.

How to Perform AC Filter Replacement?

Here is how you can perform an AC filter replacement:

  • Turn Off the AC:  Turning off the HVAC system before replacing the filter is crucial to protect the system components from damage. Removing clogged filters while the unit is running can result in dust and debris accumulating on other parts of the HVAC unit.
  • Removing the Dirty AC Filter: If you are concerned that the filter has been used less than the time recommended on the packaging, slide it out and hold it up to a light source. If little or no light passes through the filter, replace it immediately.
  • Inserting HVAC Filter Into the Frame: All filters come with packaging with directions or an arrow indicating the correct position for installation. Typically, the arrow points toward the air handler and away from the return ducts. Ensure the filter slides smoothly into the frame, and once it does, the arrow should not be pointed toward the return ducts. If the air filter is installed backward, it can damage the unit.
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Katy Willis is a writer, lifelong homesteader, and master herbalist, master gardener, and canine nutritionist. Katy is a preparedness expert and modern homesteader practicing everyday preparedness, sustainability, and a holistic lifestyle.

She knows how important it is to be prepared for whatever life throws at you, because you just never know what's coming. And preparedness helps you give your family the best chance to thrive in any situation.

Katy is passionate about living naturally, growing food, keeping livestock, foraging, and making and using herbal remedies. Katy is an experienced herbalist and a member of the CMA (Complementary Medical Association).

Her preparedness skills go beyond just being "ready", she's ready to survive the initial disaster, and thrive afterward, too. She grows 100% organic food on roughly 15 acres and raises goats, chickens, and ducks. She also lovingly tends her orchard, where she grows many different fruit trees. And, because she likes to know exactly what she's feeding her family, she's a seasoned from-scratch cook and gluten-free baker.

Katy teaches foraging and environmental education classes, too, including self-sufficient living, modern homesteading, seed saving, and organic vegetable gardening.

Katy helps others learn forgotten skills, including basic survival skills and self-reliance.

She's been published on sites such as MSN, Angi, Home Advisor, Family Handyman, Wealth of Geeks, Readers Digest, and more.

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