How regularly you should replace 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 near the residence
- Your MERV rating
For basic 1"–3" air filters, manufacturers typically 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 swap 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 changing it.
What air filter models survive longer?
Some air filters are supposed to last up to six months, while others must be replaced monthly. The thicker the air filter, the longer it will last. In general, you should look at 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 measures how well an air filter can pull particles from the air. The higher the MERV rating, the smaller the particle that will be captured by the air filter.
While a filter with a higher MERV rating will live longer, it could also restrict the airflow in your home. And you will need to switch out the filter more often. And if you own an older system, plan to replace the filter more often to extend the life of your filter.
How often do I need to replace my air filter according to thickness?
The longevity 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 benefits of thicker filters is not only do they perform longer, but they also have a better MERV rating. This means they will do a better job of eliminating the particles in your home. They also produce less air resistance, which can help your HVAC system perform more efficiently and reduce 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 often.
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 quickly clog an air filter and reduce its effectiveness. For every shedding dog you have, expect to replace the filter a month earlier than you would for a home without pets. The same goes for cats, although 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.
Although a good rule of thumb, you will have to examine 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 getting rid of their coat. Examine the air filter monthly and replace it when it looks clogged.
Here are averages that might help you figure out how often 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