How Often Do You Change HVAC Air Filters?

Depending on the type of filter you have and other several environmental factors, you should change HVAC air filters every 1-12 months. Not only will changing your air filters help your home run more efficiently, but it will also help extend the life of your HVAC system. 

So how often do you change air conditioning filters? If you’re not sure, read on– we’ll tell you.

a person inserting a new HVAC air filter

How Often To Change Air Filters

You should change your HVAC air filters every 1-12 months. The frequency with which you need to change your filter depends on a few factors, such as the type of filter you have, the amount of people in your home, and whether or not anyone in your household has allergies or other respiratory issues. 

For a standard fiberglass air filter, replacement should be every 30-60 days. On the other hand, you should change a pleated paper air filter every 90 days. 

Note: If you have pets or someone in your home who suffers from allergies, you may need to change your filter more frequently. Homes with smokers may also need to change their filters more often, as cigarette smoke can quickly clog an air filter. Or, if you live in an area with nearby wildfires, outdoor smoke can also quickly clog your HVAC filter. 

The best way to know how often to change your HVAC air filter is to check it monthly and change it when it starts to look dirty. A good rule of thumb is to check your filter every time you get your utility bill. This will help ensure that your HVAC system is running efficiently and help prolong its lifespan.

With that said, some air filters– like high-rated MERV and HEPA filters– can last six months to a year, depending on the air quality. Still, it is always best to check the filter’s replacement frequency recommendation and inspect it monthly. 

When you change your filter, make sure you put the filter into your HVAC system the right way. Match up the airflow arrows on the filter with those on your HVAC unit. 

How Do I Know if my AC Filter is Dirty?

a person showing a dirty pleated AC filter

The only way to know if your filter is really dirty is to inspect it. Otherwise, you’re just making an educated guess (or basing it on past performance). As a rule of thumb, if your air filter is visibly dirty, it’s time for a change. However, even if your air filter looks clean, it may still be full of pollutants/irritants. 

Note: One way you can check is by holding it up to bright light. If you can’t see the light shining through the filter, it’s probably time for a change. Alternatively, you can check the pressure drop across the filter with a manometer or differential pressure gauge. Every filter has a recommended maximum pressure drop before replacement. 

For example, a filter may say “replace at 1.25-inches water column” (sometimes abbreviated “in w.c.”). 

As an air filter collects contaminants, less air can pass through, and the pressure drop increases. If the pressure drop exceeds the recommendation, your system is working overtime because of a dirty air filter. 

In short, change your HVAC air filters every 1-12 months– more frequently if the air quality outdoors or in your home isn’t the best. 

What Factors Determine How Often I Should Change My Filter?

There are a few things that will affect how often you need to change your HVAC air filter, including: 

  • The type of filter you have
  • The number of people in your home
  • Whether or not anyone in your household has allergies or other respiratory issues 
  • If you have pets 
  • If you live in an area with wildfires 
  • If you smoke indoors
  • If you light lots of candles and burn incense 

Checking your filter monthly and changing it when it starts to look dirty is the best way to keep your family healthy and your HVAC system running smoothly, so check it often. 

Why You Should Change the Filter

As air circulates through your home, it passes through the heating and cooling system. The filter’s purpose is to remove contaminants from the air, like dust, pollen, and pet dander. 

A dirty air filter can cause several HVAC problems in your home, including: 

  • Reduced airflow
  • Uncomfortable temperature
  • Decreased efficiency
  • Poor indoor air quality
  • Excess wear and tear on your HVAC system

When an air filter becomes clogged with contaminants, it restricts the airflow through your furnace or air conditioner and into your home. As a result, your HVAC system has to work harder to circulate the air– which uses more energy and increases your utility bills. 

In addition, a clogged air filter can cause your furnace or air conditioner to overheat– which can lead to a complete breakdown. Regularly changing your air filter is one of the easiest ways to prolong the lifespan of your HVAC system and keep your energy bills low. 

Here are the top reasons changing your filter is critical. 

Allergens & Asthma

a woman sneezing

One of the primary purposes of an air filter is to remove allergens from the air. If you or someone in your family has bad allergies or asthma, it’s essential to change your filter regularly– especially during high pollen seasons. 

A dirty air filter can circulate allergens through your home and trigger asthma attacks or other respiratory problems like stuffy/runny noses, sore throats, watery eyes, and even skin irritation. 

In short, a clean air filter can help improve your indoor air quality and keep your family healthy. 

Bad Odors

Another sign that it’s time to change your air filter is bad odors coming from your vents. If you notice musty smells when the heat or air conditioning turns on, that’s a good indication that your air filter needs to be changed.  

A clogged air filter can cause mold and mildew to grow, leading to dangerous bacteria circulating through your home.

High Energy Bills

As we mentioned earlier, a dirty air filter can cause your furnace or air conditioner to work overtime– which uses more energy and raises your utility bills. 

In fact, according to the U.S. Department of Energy, a dirty air filter can increase energy consumption by 5-15%.

Pet Hair & Dander

a hand holding pet hair collected from an air filter

If you have pets, it’s important to change your air filter more frequently. Pet hair and dander can quickly clog an air filter and reduce the airflow in your home. As a result, your furnace or air conditioner will have to work harder to circulate the air– and (as we know) uses more energy and drives up your utility bills. 

In addition, pet hair and dander can cause allergies and other respiratory problems– so it’s essential to keep the air in your home as clean as possible. 

Smoke & Chemicals

Smoke and chemicals can also cause a build-up of contaminants on your air filter. Moreover, these contaminants can irritate your lungs and cause other respiratory problems– so change your filters often if you smoke indoors. 

Wildfires & Dust Storms

If you live in an area with wildfires or dust storms, it’s important to change your air filter more frequently. These particles can quickly clog an air filter and reduce the airflow in your home.  And just like indoor smoke, wildfire smoke and dust particles can cause allergies and other respiratory problems, too– all the more reason to check your HVAC filter often. 

Low Air Flow

a technician checking an AC’s low air flow issue

If you’ve noticed that the airflow in your home has decreased, it’s a good indication that your air filter needs to be changed. A clogged air filter can restrict the airflow and make it difficult for your furnace or air conditioner to circulate the air. 

In addition, low airflow can cause your furnace or air conditioner to break down, which usually happens on the hottest or coldest day of the year. Therefore, it’s crucial to change your air filter regularly to ensure proper airflow and prevent annoying breakdowns. 

Inadequate Cooling & Heating

Whenever your home isn’t cooling or heating properly, check the filters. Clogged air filters also make it harder for your HVAC system to circulate the cold or hot air properly. If you can’t remember when was the last time you changed the filters, a filter replacement is more than likely overdue. 

HVAC Strain and Issues

We’ve already mentioned that your AC unit and furnace have to work harder to heat and cool your home if the filter is clogged. As such, various components can require maintenance sooner than average or, worst, can break down prematurely.  

Running your HVAC system with a clogged filter is like driving in a hurry– revving your car’s engine to high RPMs, putting the gas pedal to the floor, and slamming on the brakes at every stoplight. Sure, the vehicle will perform fine with this driving method in the short term. 

But the brake pads, motor, oil, tires, etc., will all get worn down faster than if you drove like an old lady (sorry, grandma). 

Keeping the filter clean can save you some very costly repairs and discomfort. 

What Happens if I Forget to Change the Filter?

If you forget to change your air filter, eventually, the airflow in your home will decrease. Your furnace or air conditioner will struggle to move heated or cooled air throughout your home. 

And the temperature in your home likely won’t be able to reach your thermostat’s set point. 

Your energy usage will skyrocket, and so will your utility bills. And while you are uncomfortable in your home, your HVAC system will be well on its way to breaking down. 

Can I Clean My Air Conditioner Filter?

You might be tempted to clean your air filter rather than change it– but we don’t recommend it. Most filters are not cleanable– throw them out and replace it with a new one. 

If you do try to clean it, you won’t remove all of the contaminants– and it can actually cause more harm than good. When you clean an air filter, you risk damaging the filter. And if the filter is damaged, it won’t be able to do its job correctly. 

With that said, some HVAC filters are designed to be cleaned.  These filters can be washed with soap and water and then allowed to air dry. 

Consult your HVAC system’s owner’s manual (or the filter’s instructions) to see if your filter is washable– and if so, follow the manufacturer’s instructions on cleaning it properly. 

Wrap Up

As a general rule of thumb, we recommend changing your air filter every 1-12 months–  this can vary depending on the type of filter you have, the size of your home, the number of people in your household, and other factors. Checking it once a month is the best way to determine when it’s best to switch out. 

If you’re unsure how often you should change your air filter or what size and type to get, consult your HVAC system’s owner’s manual or ask a local HVAC professional. 

About The Author

Jonathon is a mechanical engineer with over ten years of experience in the HVAC industry. He has hands-on experience with all types of HVAC systems.

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