How often should you change your air filter at home

HVAC air filters are not made to last forever. They need to be regularly replaced; everybody knows that. The key question is ‘how often to change air filters in your house?’.

As you might imagine, the answer to how often should air filters be changed doesn’t have one size fits all answer. You have to change your filters anywhere between 30 days and 6 months (with the exception of vacation homes). How often to change air filters exactly?

You have to change filters when they get ‘dirty’. If you have to do that every 30, 60, 90 days, and so on, depends on the 7 factors we cover below. You will also find a simple table with recommended air filter replacement times, based on these factors.

Well, you don’t want to change them every 30 days if you don’t have to; that would require 12 filter replacements per year. You also don’t want to change air filters every 6 months (2 times per year) if they need to be changed more frequently.

Not changing your MERV-rated air filters regularly enough might increase the risk of exposure to allergens in your house, HVAC system or furnace failure, and so on. That’s why changing furnace filters often enough is very important, for example. On top of that, you will definitely have to pay higher energy bills if you don’t change the air filters often enough.

Here’s the deal:

We hate to hear “it depends” from HVAC experts but in this case, it really is impossible to say “HVAC and furnace air filters need to be replaced every 3 months” with any kind of certainty.

Below you will find a rough summarized table of how often it’s recommended to change air filters in the home (with a number of days/months for most households).

Let’s first look at the factors that influence how often should you change an air filter in your house:

7 Factors That Determine How Often Should Home Air Filters Be Changed

How regularly the air filters need to be replaced depends on a number of factors, including:

1. Types of filters. Cheaper fiberglass filters need to be replaced every 30 days. More expensive pleated air filters need to be replaced every 90 days. MERV rating doesn’t significantly impact how often should air filters in the home be changed.
2. Pets (cat, dogs, etc). Cats and dogs produce large air pollutants like air dander, pet hair, and fur. These can clog an air filter much quicker and will reduce the time of how long an air filter can remain unchanged by 1 month, or so. More than 1 pet (or a larger fluffier dog) will reduce that time even further.
3. Children in the house. With young children, you should be extra certain they breathe the cleanest air possible. That’s why it’s recommended to change an air filter in a house with children as often as every 2 months.
4. Home size. In general, large house air filters are more sparsely distributed throughout the house. That means that each air filter needs to filter out more air (above 300 CFM, for example) than in a smaller house and gets dirty quicker.
5. Allergies. If you or somebody in your household is prone to allergies, you should change air filters more regularly. The most common recommendation is to change filters every 20 to 45 days if an allergy-prone person lives in a household.
6. Indoor air quality. In houses with below-average indoor air quality, you have to change the air filters more regularly. That is because due to higher-than-average concentration of indoor air pollutants, filters have to work extra hard to filter them out and reach their capacity quicker.
7. Air pollution levels around your house. If you live nearby a busy street or even the factory, every time you open the door or a window, you will allow for air pollutants to enter your home. In this case, is better to change air filters 1 week earlier than you usually would.

As you can see, pinpointing exactly how many times per year should air filters be replaced can be daunting. We’re going to simplify it.

Here are the best practice recommendations for how often to change the air filters in the house:

General ‘How Often Should You Change Your Air Filters In House’ Recommendation

The best we can do is make the best estimates on how frequently home air filters can be changed based on the 7 factors listed above.

As you can see from the table above, it is enough to change air filters in non-occupied suburban homes with no pets once per year (every 12 months). When we add pets, people, city center locations, and so on, you have to change filters more often (down to 20 days).

Here is the full table with recommended air filters replacement times for pleated air filters:

Home Situation:	How Often To Change Filters?	Comment:
Non-occupied suburban house without pets	Every 12 Months	Without occupants, you can be less worried about indoor air quality
Occupied suburban house without pets	Every 90 Days	No pets = no danger, suburban = no busy streets
House with 1 pet (dog, cat)	Every 60 Days	Big pet dander clogs the filters quicker
House with 2+ pets (dogs, cats)	Every 30-55 Days	More pets equates to more pet dander
Apartment in the city center	Every 45 Days	Air quality in city centers is worse than in suburban areas
House with an allergy-prone person or children	Every 20-45 Day	With allergies, you need higher indoor air quality

These are general recommendations. It makes sense to check what kind of how you have so you know more precisely how often to change filters.

In practice, it’s always the best practice to check on how dirty your home air filters or furnace filters are from time to time. When you start seeing grey dust settling on the entire surface of home air filters, then it’s time to change them.

We hope this helps a bit.

• 7 Factors That Determine How Often Should Home Air Filters Be Changed
• General ‘How Often Should You Change Your Air Filters In House’ Recommendation
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