When Should I Change My Air Conditioner's Air Filter at Home?

February 26, 2015

Looking for the quick answer? Check out our FAQ on "How often to change the air filter".  

Occassionally we’re asked what is the most important thing that Boise area homeowner's can do to ensure efficient functionality of their air conditioning and heating system between their scheduled tune-ups? Our advice is simple; remember to change the heating and air conditioning air filter. Changing furnace and return air filters is crucial to the effectiveness of your HVAC system, in addition to your home's air quality. Did you know indoor air pollution is among the top five environmental health risks? You probably don’t consider it as you sit and watch TV, but this is the air you breathe day and night. Changing the air filters is not a tough thing to do for most Boise homeowners, but there are usually two hurdles to actually completing this job:
  1. Determining just how often to change your furnace or air conditioner filter.
  2. Changing them when you’re suppose to.

When To Change Your Air Filters

Most filters have a recommended guideline on the box or plastic. It may say "Lasts up to 3 months" or "Change filter every 90 days". Check out the filters at the store and you'll see that some are engineered to only last one month, while other manufacturers (like Honeywell) have created media air cleaners with filters meant to be swapped once every 6-12 months. The norm seems to be once every 3 months for most higher quality filters, but we have a rule of thumb that we recommend our readers to go by. If it's dirty, change it! A dirty air filter can add or cause damage to expensive equipment, like your compressor, so it's better to change it out more often than neglect it. If you want to follow the manufacturer's recommended limit, we suggest marking the date on the filter when you swap it out, and setting a reminder for yourself in your phone or on a calendar. Also note that your filter manufacturer might have a different recommendation from your HVAC system manufacturer.

Figuring out how often to change your air filters hinges on several factors:

  • Type of filter your A/C system requires
  • The overall air quality of your Boise area home
  • Pets – Birds, cats, dogs, hamsters (do you have one?), etc.
  • Number of occupants in the house
  • How much construction is taking place in the neighborhood around your home

For your standard 1"-3" air filters, the manufacturers basically say to change them bi-monthly, which is in fact a great rule of thumb. But generalities may not be suitable for your specific needs. If you suffer from light to moderate allergies, you may need to upgrade the air filter or change them even more often than OEM specifications. On the other hand, if you're in a less populated area, own a less occupied home (like a vacation home) or an area with few automobiles and trucks, replacing your air filters each year may be quite sufficient. Why should you factor in your pets? They have a tendency to shed, which can clog your air filter fast. Clearly, the air filter is just doing its job by containing pet hair and dander, but extremely dirty filters can cause seriously reduced HVAC performance.

In summary:

  • Vacation home or single occupant homes without pets or allergies: Change 6-12 months
  • Average suburban home without pets: Change every 90 days
  • Add a dog or cat: Change every 60 days
  • More than one pet or have allergies: Change every 30-45 days

How To Remember To Change Your Air Conditioner's Air Filters

It's simple; sign up for the Service Experts Email Club. This is a convenient way to get money-saving discounts and other helpful information on your smartphone, tablet or desktop. But wait… there’s more, your email subscription preferences let’s you set a reminder to change your Boise area home's air filter every 30, 60, 90, 120 or 365 days, or any date you find most convenient.

How to replace your return air filter

Most people know how to replace the air filter in their unit, but some residences have an extra filter in the return vent. Whether you have one or not is dependent on the HVAC manufacturer's recommendation. Your HVAC is designed to handle a set amount of pressure in your home, and the more filters you have the harder the blower motor works, which can reduce the lifespan of your system if it isn't designed for it. Learning whether you have a return filter and replacing it is simple:

  1. Go to your return air vents.
  2. Some covers have screws and some have tabs. Unscrew or pull tabs to take off the wall.
  3. Look for a filter. If one is inside, pull it out and write down the size.
  4. Verify the filter type is the one recommended by the manufacturer.
  5. If filter is dirty, replace with the manufacturer's recommended filter of the same size and type.
Incredible though it may seem, filters can really affect your home's airflow, which is why we recommend checking in with the manufacturer. A more expensive HEPA filter that is designed to catch finer particles will restrict airflow more than a cheaper filter. With restricted airflow comes increased pressure on your system, so you need to verify that your HVAC system was made to handle it. Otherwise, you might experience uneven heating and cooling efficiency in your home, and system parts may break down much faster than otherwise.
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