man changing dirty air conditioner air filter from return vent in wall of home

Your air filter should be changed every 1 to 3 months, depending on the type of filter. Proper maintenance of your air conditioner and furnace system will ensure better air quality in your home, increase the lifespan of your HVAC unit, and consume less power, resulting in lower energy bills.

It would be more straightforward if all air filters needed to be changed on a set schedule, but, unfortunately, various factors impact the frequency with which a filter needs to be changed.

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How Often to Change an Air Filter

How often you change your air filter depends on a few fundamental factors – number of pets and household members in a household, location, size of your home, time of the year, allergy sensitivity, and type of filter.

Number of Pets and Household Members

Air filters need to be changed more frequently if you have a larger household. Families with younger children and elderly family members should change their filters every 2 to 3 months to ensure your family is safe from germs and other potentially harmful airborne contaminants.

If you have dogs, cats, or other animals, it's best to replace your filter more often. Pets are a significant factor as they shed hair and dander that can quickly accumulate and obstruct airflow. If you have an indoor pet, you should change your air filter every two months and increase the frequency to every 15-30 days if you have multiple pets and allergy issues.

Where Your House is Located

Your geographical location can also determine how often you should change your air filter. If you live in an excessively hot and humid or dusty region, your air conditioner will probably run for a longer time. The more your AC system runs, the more air blows through the filter. More significant amounts of particulates get trapped when more air moves through the filter. In this instance, you should change the air filter more often.

On the contrary, if you live in a mild climate and use your air conditioner for less than five hours a day, changing the filter can be avoided for a few additional months.

The size of your home

The size of your home can play a significant role in the frequency of air filter replacements. If you live in a larger house, more air is required to circulate through your air conditioner to cool it down. The more air sucked through the air filter, the dirtier and dustier it will get. On the other hand, smaller homes will demand less air pumped, requiring less frequency of replacing the filter.

Time of the Year

During peak winter and summer months, your heating and cooling system is operating at its highest capacity, so you should consider changing your air filter more frequently to ensure your unit runs smoothly. 

Air Quality in Your Home 

As anticipated, if the air quality in your home isn't optimal, you will need to replace your air filters more often. The number of pets and family members with allergies will require you to change your air filter more frequently. If an occupant smokes, replacing the air filter can increase air quality within the home. 

Regular maintenance of your home's HVAC system is essential to operate efficiently. Proper care will improve the air quality in your home, increase the lifespan of your unit, and require less energy to help lower your bills. 


Individuals with allergies, asthma, or other respiratory conditions are sensitive to airborne particles. They'll need quality air to lessen the chances of worsening the situation. To guarantee your system is pumping only clean air, change your filters every 30-45 days.

Type of Filter

Some air filters are more effective than others. There are two main types of air filters, and the one in your HVAC unit will determine how often it needs to be changed.

Fiberglass Filters


1 month

MERV Rating:

1 - 4

Fiberglass AC filters are a disposable type of low-cost filter without hampering quality and efficiency. This type of filter needs to be replaced every month, or even quicker, depending on the factors mentioned above.

Pleated Filters


3+ months

MERV Rating:

5 - 13

Pleated air filters are thicker, high-quality filters that are very effective in trapping particles and last up to four months, depending on the season and usage frequency.

Washable Filters


5-10 years

MERV Rating:

1 - 4

If you have electrostatic or washable filters, they should be washed, dried, and re-installed once a month. Generally, they are more eco-friendly and can last 5 to 10 years if cleaned and reused appropriately.

HEPA Filters


6-12 months

MERV Rating:

17 - 20

If you or a family member in your home has allergies, a HEPA filter is a good choice. According to the EPA, high-efficiency particulate air filters can remove 99.7% of dust, pollen, mold, bacteria, and any airborne particles in your indoor air. Depending on other factors, you should change HEPA filters once a year

While various factors affect the frequency of air filter replacement, a good rule of thumb is to check your air conditioner filter for excess dirt and grime buildup every 30 days to determine whether it needs a replacement. Reference the air filter packaging for the expected lifespan of the filter. Some manufacturers recommend replacing air filters every 30 to 60 or 90 days, depending on the type of air filter. Call your local HVAC professional or the air filter manufacturer if there's ever a question to determine its lifespan.

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How to Change an Air Conditioner Filter

Homes can have different air condition systems with varying filters of air.

If you have a return air vent filter, follow these steps:

  1. Locate air return vent
  2. Turn the unit off to prevent the circulation of unfiltered air
  3. Open the vent carefully - this may require unscrewing
  4. Remove the air filter while taking care that the arrows are facing toward the system
  5. Insert the new air filter. Make sure the arrows are facing the right way. Arrows usually indicate which direction the air pulls, and you’ll want the air to pull into your system, not away from it.
  6. Close the vent carefully
  7. You are ready to turn the AC back on again!
Senior male reaching up to open return air vent for air conditioner filter in ceiling
A person changing an clean air filter in an air handler furnace

If your home has an air handler/furnace filter, you need to:

  1. First, make sure you power off your HVAC unit
  2. Locate the air filter – this could be near the air supply and remove the panel
  3. Remove or unlatch the door/filter cover
  4. Carefully slide out and remove the used filter
  5. Take care of the airflow arrows while removing
  6. Install the new filter, making sure the directional arrows are facing the HVAC unit, in the direction of airflow
  7. Replace the panel cover, and you are done!
  8. Turn the AC back on and enjoy uninterrupted cooling.

Why Should You Change the Air Conditioner Filter?

It is vital to switch your air filters regularly to improve the air quality and protect the sensitive components of the air conditioner. Changing your air filter is one of the easiest and most effective ways of ensuring the operational efficiency of your heating and cooling system. Neglected air filters can cause:


  • Increased energy bills— When an air filter is blocked, your air conditioner unit has to work harder to pull air through to cool the room. Working harder causes it to run for extended periods, increasing your home's energy. According to the U.S Department of Energy, replacing a dirty, blocked filter can lower your air conditioner's energy utilization by 5% to 15%.

  • Health concerns—If a filter isn't working correctly, dust, pollen, and other allergens can spread throughout your home and increase allergy attacks and respiratory conditions.

  • System failure—An air conditioner system has to work hard to pull air through a dirty filter. Constant strain on your HVAC system can cause it to break, causing you to pay for expensive repairs or replacements.

Signs You Need to Change Your Filter

Your air conditioner continuously circulates air, passing through the air filter. Keeping the filter clean or frequently replacing it is vital to extend your HVAC system's lifespan. 

There's no straightforward answer to how long the air filter can function efficiently before needing a replacement. However, there are some obvious signs that your filter needs a replacement:

closeup of male hands inspecting HVAC unit is warm to touch

1. HVAC Unit Overheating

A blocked air filter will cause your air conditioner system to work harder and longer because it has to use more energy to move the same amount of air through the filter. You should inspect the air filter first if you notice that the unit is warm to the touch.

If you switch out the filter and your air conditioning unit still isn't cooling down, call your local HVAC professional to look at it. You may have a more significant situation.

african american woman blowing nose because of allergies caused by dirty air filter

2. Allergies

Air conditioners filter pollen and other airborne pollutants and are your first defense against contaminants. If you or a family member suddenly start having allergy symptoms, such as itchy and red eyes, scratchy throat, sneezing, and sometimes even skin reactions, you should check the air filter. If the air filter is dirty and clogged, the lack of air circulation can create pressure and force outdoor allergens into your home.

Caucasian man looking at high energy bills caused by dirty air filter

3. Energy Bills

A buildup of contaminants and debris, including dust and allergens, can clog air filters and diminish the air circulation throughout your home. As the AC unit works to counteract the effects of this excess debris and dust particles, it can work overtime, increasing energy bills. 

woman's finger with dust from excessive dust on table caused by dirty air filter

4. Excessive Dust

An air filter removes dirt and dust from the air before it circulates through your home. You're overdue for a filter change if you see dust building up around your home's output vents, fan blades, curtain rods, or nearby tables and cabinets.

Caucasian woman forgot to change air filter

5. Can't Remember the Last Time You Changed It

Generally, your air conditioner air filter needs to be replaced between one to six months. At a minimum, change the air filter every 30 days during peak season. If you can't remember the last time you replaced it, you're likely overdue.

closeup of a finger with dust from air filter white sheet test

6. White Sheet Test

Another way to decide whether your air filter needs to be changed is by hanging a white sheet a few inches away from one of the vents in your home and leaving it in place for an hour.

Take a glimpse at the white sheet to see if it has turned gray or black. The dirtier the sheet gets, the more likely your air filter needs changing.


Although various factors can determine the frequency, regularly replacing the filter in your air conditioning unit ensures your AC system runs efficiently and, most importantly, maintains quality air in your home.

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