How frequently you should exchange your air filters can depend on the following:
- Air filter model
- Overall indoor air quality
- Number of pets
- Household size
- Air pollution levels and construction around the residence
- Your MERV rating
For common 1"–3" air filters, manufacturers generally instruct you to replace them every 30–90 days. If you suffer from light to moderate allergies, you can install a better air filter or replace them even more regularly.
The shortest answer to "how often should I replace my air filter?":
If you don't have a smoker or pets in the home, and your filter is the frequently sold 1" filter with a MERV rating of 4, you should be able to wait up to 90 days before replacing it.
What air filter models last longer?
Some air filters are manufactured to last up to six months, while others must be replaced monthly. The denser the air filter, the longer it will last. As a whole, you should check the thickness of the filter rather than the brand. You also need to look at the MERV rating.
The MERV rating is a scale that goes from 1-20 and assesses how effectively an air filter can pull particles from the air. The better the MERV rating, the smaller the particle that will be caught by the air filter.
While a filter with a higher MERV rating will last longer, it could also restrict the airflow in your home. And you will have to exchange the filter more often. And if you own an older system, plan to replace the filter more often to preserve the life of your filter.
How often do I need to exchange my air filter based on thickness?
The life span of an air filter also depends on its thickness. A 1" filter will have to be replaced more often than a 4" filter.
- A 1" pleated air filter should be replaced every 30-60 days.
- A 2" pleated air filter should be replaced every 90 days.
- A 3” pleated air filter should be replaced every 120 days.
- A 4" pleated air filter should be replaced every 6 months.
- A 5” or 6" pleated air filter should be replaced every 9-12 months.
One of the advantages of thicker filters is not only do they perform longer, but they also have a higher MERV rating. This means they will do a better job of filtering out the particles in your home. They also create less air resistance, which can help your HVAC system function more efficiently and decrease wear and tear on components including the blower motor.
If you have a whole-house air purifier, you will also need to replace the filters more frequently.
How often should I change my air filter if I have a dog or cat?
If you have pets, you might have to replace your air filter more often. Pet hair and dander can swiftly clog an air filter and reduce its effectiveness. For every shedding dog you own, prepare to replace the filter a month earlier than you would for a home without pets. The same goes for cats, even though they don't shed as often as dogs. If you have a hypoallergenic or non-shedding dog or cat, you might not have to replace your air filter as often.
Though a good rule of thumb, you will have to inspect your air filter more frequently to see if it needs to be replaced. Dogs don't shed the same amount year-round. They shed more in the spring and fall when they are blowing their coat. Study the air filter monthly and replace it when it seems clogged.
Here are averages that might help you know how regularly you should get a new air filter at your home:
- Vacation house or one occupant and no pets or allergies: every 6–12 months
- Normal suburban home without pets: every 90 days
- One dog or cat: every 60 days
- More than one pet or if anyone has allergies: 20–45 days