How Often Should You Change Your HVAC Filters?

air filter being replaced in a vent on a home ceiling

Changing your HVAC air filters is an unavoidable part of being a homeowner and a vital piece of home maintenance. If you don’t do it, it can have consequences for your home and household. Every three months is a good baseline, but various factors can affect how frequently you need to change your HVAC filters, such as how many pets you have and whether allergies are a concern. 

How Often to Change Your HVAC Air Filters

Photo Credit: ronstik / Canva Pro / License

Changing the air filter every 90 days is a good rule of thumb, but it is only a general guideline that doesn’t account for homes’ individual needs. Every home is different, and will need their filters changed more or less often. There are several factors that can affect how often your specific HVAC needs to have its filter changed.

Factors That Affect Frequency

There are a few factors that affect how frequently you’ll need to replace your cooling system’s air filter. Most of them are related to your household and the people living in it, but some have to do with the local area you live in. Here are some factors that may affect how frequently your filter needs to be replaced.

Filter Type

The type of furnace filter you use has a lot to do with how frequently you need to change it. If it’s not powerful enough, you may find yourself changing it more often. The same can be said if you’re buying filters with an insufficient MERV rating.

Home Size

The larger your home, the harder the HVAC has to work to condition its indoor air. That means that the system’s filters will get dirty faster and need to be changed more often. Smaller homes, on the other hand, won’t need their air filters changed as frequently.


Another factor that affects how often you need to change your air filter is how many people and animals are living in the house. The more people, the more often you need to change your filter due to the increased amount of airborne contaminants they bring. Pets with fur, such as dogs and cats, will especially make the air dirtier due to dander and bacteria.


While having allergies doesn’t affect how dirty your air filter gets, it does affect how often you need to change the filter. It’s important to keep the indoor air quality up for people with allergies, asthma, or other lung and breathing issues. Therefore, it’s a good idea to change the HVAC’s air filter more often to keep your household healthy.

Air Quality

Air quality also affects how often you need to change your filter. Specifically, the quality of the outdoor air. Outdoor air quality affects your indoor air quality through open doors and windows as well as ventilation systems. The dirtier the air in your local area is, the harder your HVAC has to work to purify your indoor air, which means your filter gets dirtier faster.


The time of year also affects how often you need to change your HVAC’s filter. During the summer, people are more inclined to keep their windows open, which lets in outdoor contaminants like pollen, while they’re more likely to keep them closed in the winter. There will also be higher amounts of pollen during different times of year, which can affect the indoor and outdoor air quality.


Finally, a big factor that affects how often you need to change your HVAC filter is how clean you keep your house. If you let dust and dirt build up, particulate matter gets into the air and is sucked into your HVAC, where it’s caught by the filter. If you want to make your air filters last longer, keep a clean house and don’t let dust pile up.

Signs You Need to Change Your HVAC Filters

Photo Credit: Backyard Productions / Canva Pro / License

If you have doubts on when to change your HVAC filter, you can look for a few signs. Here are some telltale indicators that you need to change your filter:

  • Lower air quality
  • A musty smell coming from the vent
  • Hold your filter up to the light. If no light passes through it, the filter needs replacing.

Why You Need to Change Your Air Filters

Changing your AC filters is a necessity. If you don’t change it, you can expect various problems with your household and HVAC system. Here are a few consequences of not changing your air filters:

  • The dirty filter becomes a fire hazard.
  • The air coming from your vents will have a musty odor.
  • Your HVAC will have to work harder to move air through the dirty filter, which means lower efficiency, worse temperature control, higher energy bills, and decreased lifespan for the system.
  • Mold may develop in your HVAC or air ducts.
  • The dirty filter can collapse and possibly clog and damage the system.
  • The indoor air quality in your home will suffer.

What Type of Filter is Best?

Photo Credit: spates / Canva Pro / License

Different households have different air filter needs, so different types will suit them better. If you or other members of your household have allergies, for example, it’s best to get one designed to filter allergens. On the other hand, if you have a lot of pets, you need one designed for pet hair and pet dander.

However, even though certain households have different filtration needs, there are some types of filters that are objectively better than others. For example, pleated filters outdo fiberglass ones across the board, so that’s a good way to narrow down your options. 

You can also check the MERV rating, or Minimum Efficiency Reporting Value, which is a scale of 1 to 20 that measures how effective a given air filter is. Other than that, look for quality filters from names you trust.

How to Change Your HVAC Filter

Changing an HVAC filter is a very simple and easy process. It doesn’t require any special tools or equipment, and you won’t need to get a technician to come out and do it for you. All you need to do is follow the steps below:

  1. Obtain a new filter. If you don’t have one already, you can find them at many retail stores.
  2. Shut off your HVAC system. You shouldn’t try to change the filter while the AC or furnace is running.
  3. Remove the old filter. It might be in the HVAC itself, behind one of your supply vents, or both.
  4. Insert the new filter. Make sure it’s in correctly and not loose.
  5. Restart your HVAC. Wait a bit and make sure it’s running properly. If you notice anything unusual, you may need to adjust your filter.
  6. Dispose of the old filter. Throw it out in the outside garbage to ensure none of the dust and debris trapped inside escapes out into your indoor air.

FAQ About Air Filters

Can I run my HVAC without a filter?

You can, for a short while, but it’s not recommended. Running your HVAC unit without a filter means that all the particles in your home will just get recycled endlessly and keep lowering your indoor air quality. Dust and debris previously trapped in the system may also blow into your home, which will worsen the problem. You even run the risk of permanent damage to your HVAC due to all the contaminants getting into parts of it they shouldn’t.

Can I use two HVAC filters at once?

No, you should not try to use more than one filter at a time. This restricts the airflow and creates conditions similar to a dirty, clogged filter. One filter is plenty, and you will likely have trouble fitting two filters in at once regardless, so don’t try to use multiple filters at a time.

What does it mean if my filters are getting dirty faster than usual?

If you’re going through filters faster than you used to, it may be due to a change in your home or local area. New people moving in, a new pet, or different weather or changing seasons can all affect the rate at which your filters absorb pollutants. If nothing has visibly changed, do a thorough examination of your unit and ductworks, as it could indicate mold or another problem somewhere in your HVAC system.

Find a Pro

If you don’t change your HVAC filter on a regular basis, you risk poor air quality, and therefore a reduced quality of life. Keep track of your filter changes and check it if you believe it’s not doing its job effectively.

If you’re having trouble with your air conditioning system, contact your local HVAC professionals. They can service your unit and ductworks so that your air stays clean.

Main Photo Credit: Backyard Productions / Canva Pro / License

Austin Geiger

Austin Geiger is a writer who's passionate about home care. He enjoys writing about home maintenance practices, as well as projects to turn an outdoor space into a backyard paradise.