Here's Why You Should Change Your Air Filter Every 3 Months

What if one small, often forgotten task could make your HVAC system run smoother and, at the same time, save you money on your energy bill?

It is possible! That task? Replacing your air filter. You know, those things tucked away inside your furnace and air conditioner. Most of us forget about them for months or maybe years.. but a little clogged filter can really mess things up in a big way.

So, how often should you be replacing them to avoid trouble? The short answer is every 3 months (or every 90 days).

However, it's sometimes not so straightfoward. Keep reading to find out how your environment can heavily affect this.

How often should I (really) change my air filter?

The real answer is that it depends.

A general rule of thumb for pleated air filters is to replace your filter every 90 days. As your filter traps more dirt, dust, and allergens from the air, filter efficiency decreases. 

Typical recommendations range from every 30 days for cheaper fiberglass filters (which also don't work as hard at filtering out your air).  

Note: These estimates assume average use and take into account the type and size of your filter.

how often to replace your hvac air filter

"Properly maintaining your HVAC or central air system and upgrading your HVAC filters can improve your home’s air quality." (Source: American Lung Association) 

3 Factors That Affect How Often to Change Your Air Filter 

1. Does someone in your home have asthma and/or allergies?

Those with asthma and/or allergies are much more sensitive to airborne particles than those without. If you have an asthma- or allergy-sufferer at home, change your filter every 6 weeks to ensure indoor air quality is at its best.

2. Do you have pets?

Cats and dogs shed and have odors that can build up in your space, making it necessary to change your filter every 2 months. Generally, cats and dogs shed at pivotal moments-- most when winter turns to spring and summer turns to fall, which are key times to replace your filter.

3. Do you have young children?

Superior indoor air quality is especially important with kids around. Keep your home clean and air quality under control by replacing your vacuum filter every 2-3 months.

factors in how long to change your air filter

Factors that can affect your HVAC air filter's lifespan include:

ac units require consistent maintenance to ensure longevity and cooling powerThe rate at which you use your heating and/or cooling system

If you live in a temperate climate and use your heater and/or air conditioner up to a few hours every day, a single filter can last you from a whole season to an entire year. If your HVAC system is running on a near-constant basis, however, change your filter every few weeks (especially if you're using a cheaper fiberglass filter).

The size of your home

Furnaces and air conditioners in smaller homes need to pump less air for the same amount of temperature change, which may mean less frequent filter changes. These appliances are often built with smaller filters, though, and thus may need to be changed just as regularly as a filter in a larger home.

The air quality within your home

The air within or outside your home will also affect your filter's replacement cycle. Pets or poor air quality, for example, will require you to replace your air filter more frequently.

How to Tell When Your HVAC Air Filter Needs Changing

Any use will lead to some amount of dirt being trapped in your air filter - that's its job, after all.
So how do you know when your filter has trapped too much dirt and needs to be replaced?

Repair Man Image

There's no strict guideline, but if your filter shows only a subtle layer of dirt under which the filter's material is still visible, your filter is in fine working order. Once it gets much beyond that point, it's ready to be changed out. If there's a visible coating of dirt covering most of your filter's surface that is adequately thick to obscure the filter material itself, that's a sign that your filter has been in your HVAC system far too long.

Every few weeks, take out your filter and give it a look! Is there a musty odor? Is the filter covered in dust? If in doubt, it's always best to err on the side of replacing your filter. They're relatively inexpensive, and that small cost to keep your heating and cooling vents clear will be well worthwhile when your energy bill comes due. If it's been a while since you've changed your filters, we can help you find the right size, brand, and type of HVAC air filter for your furnace and/or air conditioner.

Ready to replace your filter? Click here and get your system back to clean efficiency!


Frequently Asked Questions About Changing Air Filters

How do I know when my air filter needs to be replaced?

There are often obvious signs that your air filter needs changing. Here are the 7:

  1. Dust and debris accumulating on your intake vents
  2. Dust and debris accumulating near your output vents, often on the ceiling and walls nearby
  3. Dust accumulating on fan blades, curtain rods, on top of cabinets, indicating that there is an excess of dust in circulation
  4. Noticeable loss of cooling power in your AC system
  5. Sounds of excessive strain when your AC system starts up
  6. Longer periods of run time for your AC system to cool to desired temperature
  7. Indicator on your AC controls telling you to change your air filter

Just go by the rule: when in doubt, buy a replacement air filter and change it out.

READ MORE: How Often Should You Change Your Furnace Filter

What are the symptoms of a dirty air filter?

Symptoms of a dirty air filter can include:

  • Dust and debris accumulating on your intake vents
  • Dust and debris accumulating near your output vents, often on the ceiling and walls nearby
  • Dust accumulating on fan blades, curtain rods, and on top of cabinets, indicating that there is an excess of dust in circulation
  • Noticeable loss of cooling power in your AC system
  • Sounds of excessive strain when your AC system starts up
  • Longer periods of run time for your AC system to cool to desired temperature

Does changing the air filter make a difference?

Yes, changing your filter has several major impacts on your HVAC system’s ability to cool your house and the overall quality of your air. When you change your air filter, you allow more air to flow through your system with less power usage resulting in better circulation, cleaner air, and a lower electricity bill.

What happens if you don't change your HVAC filter?

Neglecting to change your HVAC filter can lead to some real issues. A clogged filter restricts airflow, forcing your system to work overtime and guzzling more energy (hello higher bills!). It also puts extra strain on your equipment, potentially causing breakdowns. Plus, a dirty filter can't trap dust and allergens effectively, so your indoor air quality takes a big hit.

How do you know when to change your HVAC air filter?

Do a visual inspection if you think it might be time to change it. You can do this inspection by comparing your filter to a sheet of white paper. If the filter is clearly dirty, it's time for a fresh one. Other tip-offs are weak airflow from your vents, extra dust accumulating around the house, or if your system just isn't heating or cooling as effectively as it should. Some filters also have a handy color-change indicator to take the guesswork out.

Do I need to change my air filter every month?

First things first. Do you have fiberglass or pleated? If they're pleated, they'll last longer than a month. Changing monthly may be overkill for some homes, but in certain situations, it could be beneficial. If you have pets that shed, allow indoor smoking, or if allergies are an issue, more frequent swaps help keep the air clean. Living in a high-traffic home or an area with poor outdoor air quality are other cases where monthly filter changes make sense.

Why is my air filter black after one week?

A black air filter after just a week is a red flag for poor air quality. Possible culprits include indoor smoking, heavy shedding by pets, ongoing nearby construction, or simply poor air quality outside. It’s crucial to address these issues and keep up with regular filter changes.

How long can an AC run without a filter?

It's never a good idea to run your AC without a filter. Doing so allows dust and debris to accumulate on the evaporator coil, cutting off airflow and reducing efficiency. In fact, running filterless can potentially damage your AC system. Using a clean filter is essential to protect your equipment and indoor air quality.

Do I need to change my air filter if it doesn't look dirty?

Even if your filter appears clean, those tiny particles can still accumulate and clog it up over time. Changing your filters every 3 months is the way to maintain proper airflow, efficient operation, and great indoor air quality throughout your home.

Why does my air filter get so dirty every month?

If your furnace filter seems to get filthy that seems too be too fast each month, there could be a few factors at play. Lots of dust, pet hair, or indoor air pollutants (like smoking) accelerate dirty filters. Using the wrong filter type or efficiency rating can also make your filters dirty faster.


How Often Do I REALLY Need to Change My Air Filter?