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How Often Should I Change My Air Conditioner Air Filter?

Throughout the next year or so we'll explore HOW things in the air conditioning and heating biz work and HOW to handle some common HVAC problems and situations, in a new HOW series of blog posts. Keeping your HVAC system running smoothly keeps you from having to rely on an air conditioning repair company to fix your system. I’ll start things off with one of those topics that’s so common, but you just might not really know much about it.  

Sometimes I'm asked what is the most important thing that homeowner's can do to protect their air conditioning and heating system between their regular PLUS Maintenance Tune-ups. It's a simple question with a simple answer; remember to change the heating and air conditioning air filter. Changing furnace and return air filters is crucial to the proper performance of your HVAC system, not to mention your home's air quality. Did you know indoor air pollution is one of the top five environmental health risks?* I know it's the last thing on your mind, but this is really important stuff. Changing the air filters is not all that hard for most homeowners, but there are usually two obstacles to actually getting it done:

  1. Knowing just how often to change your furnace or air conditioner filter.
  2. Remembering to change air filters when needed.

You can read some of the basics about filtration ratings here, and in a later post in this HOW series I'll discuss the various types of filters. For now, let's talk about these two big hurdles.

1. When To Change Your Air Filters

Simple, when they're dirty. Ok, now here's how to... Wait, not enough info? Ok, well... you can read the rest of this section for the details, or just skip over it if you're good to go.

Ready to dive in? Good, I like that. How often to change your air filters can depend on several factors:

  • the type of air filter you are using
  • the overall air quality of your home
  • pets, pets, pets..
  • occupancy of the home, and
  • the level of air pollution and construction around the home
  • ...and did I mention pets? Oh yes, pets.

For your standard 1"-3" air filters, the manufacturers basically tell you to change them every 30-60 days, which is actually a great rule of thumb. But general rules aren't always for everybody. If you suffer from light to moderate allergies, you could upgrade the air filter or change them even more often. Or, if you're in a more remote area, less occupied home (like a vacation home) and there are fewer cars around, annually may be quite sufficient. Why do pets matter so much? They have a tendency to shed, which can clog your air filter quick and with great success. Of course the air filter is just doing its job by capturing pet hair and dander, but extremely dirty filters can cause extremely weak HVAC performance.

I know, you skipped the previous paragraph but just have to have that quick and short guideline, so here it is:

  • Vacation home or single occupant w/o pets or allergies: 6-12 months
  • "Average" suburban home w/o pets: every 90 days
  • Add a dog or cat: every 60 days
  • Add more than one pet or have allergies: 30-45 days

2. How To Remember To Change The Darn Things

It's simple; sign up for the Service Experts Email Club. When you do, you can elect to receive (or not) great email coupons and newsletters with a lot of tips and discounts on AC repairs and tune-ups. But here's whats cool, in your subscription preferences you can also select to be reminded to change your home's air filter by email every 30, 60, 90, 120 or 365 days, or even on the date of your choosing... whew. You can easily subscribe to the Service Experts Email Club for free at your nearest location's home page. You'll then get an email inviting you to set up your email preferences. Just click the link in the email and choose the email options and air filter reminder intervals you want.

I hope I've helped to shed some light on the dirty little subject of getting around to changing dirty air filters. If you have heating and air conditiong related questions you would like answered, post it on our Facebook fan page, or just enter a comment with your question for Sam.


For more information of filter types peruse my other blog posts. To answer a few questions though, the cheapest filters essentially are only meant protect the indoor unit from larger particles of dirt between tune-ups. They really do not adequately cleanse the air or help with allergies very much. Thicker or more dense filters help more, and do not make the heating and cooling equipment 'work harder'. The equipment should will work the same as before, however a maintenance tune-up is recommended to ensure the performance is what it should be.

Dirt can get trapped in carpeting more than a solid surface floor. But, with 5 pets, you will likely still have the need to change your air filter very often. When you do you may notice you sneeze less and breathe easier!
8/5/2013 8:29:07 AM

My intake filter was chnged 2 weeks ago and today I noticed a differnce in air temp. I checked filter and sure enough dirty! I pulled up carpeting several years ago, so woodne floors. I have 5 mini there is dirt. If I put down carpet tile, do you think this will help keeping the dirt down?
6/23/2013 7:09:24 PM

Mobilus Oro Kondicionieriai
Air conditioner filters are to be changed before each summer season.
6/3/2013 8:11:47 AM

The filters I buy say up to 3 months....

Can that possibly mean: Up to 2160 hours of operation?

2/9/2013 12:00:59 PM

Does anyone ever talk about hours of fan operation?

When a manufacturer says "up to 3 months" , does that mean up to 2160 hours?
2/8/2013 12:27:05 PM

Mark Schell
How about the MERV 4" (or 5") filters? I know, it depends on our conditions, but lets say "standard conditions" - no pets, no construction, 60-year-old house..... What would a good range be?
2/7/2013 2:43:54 PM

SE Slim
I generally have to change mine every 30 days. I have 600 - 700 sq feet and several cats. I have an unusual size filter (14x18) so I don't really have my choice of good filters, unfortunately, as I would prefer something that catches a lot of the dander and other dirt. I clean up daily but it's still in the air every time I pet a cat. I also live in the city but in a more remote area and my building is pretty solid so I don't get much outside gunk in my filter.
7/19/2012 5:03:22 PM

Barbara, it might be a bit out of the ordinary but there could be some underlying reasons why. First, if you have been experiencing milder temperatures in your area and have reduced your cooling and heating, the reduction in airflow across your filter would definitely be a contributor. To ensure that your filtration system is always working at its optimum level, you can switch your thermostat fan setting to “ON” to keep a continuous flow of air across your filter at all times. Also, the removal of certain sources of airborn particulates could lead to a reduction in the particulates you see captured by your filter.
4/28/2011 1:22:30 PM

Barbara Lallement
I just took my filter off that I had put up on March 9th. It has no spect of dust on it. Isn't that unusual ? We have been having very high winds.
4/28/2011 10:38:43 AM

tilak ahuja
Aha good one on change the ac filter. Air conditioner filters are to be changed within 3-4 months.
3/3/2011 1:43:46 AM