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

February 26, 2015

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

Occassionally we’re asked what is the best thing that San Antonio area homeowner's can do to ensure efficient functionality of their air conditioning and heating system between their seasonal tune-ups? It's a simple question with a simple answer; remember to change the heating and air conditioning air filter. Replacing furnace and return air filters is critical 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? We know it's the last thing on your mind, but this is really important stuff. Changing the air filters is not difficult for most San Antonio homeowners, but there are usually two challenges to actually accomplishing this task:

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

When To Change Your Air Filters

Most filters have a recommended guideline on the packaging. It may read "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 designed to only last a month, while other manufacturers (like Honeywell) have released media air cleaners with filters meant to be swapped once every 6-12 months. The standard seems to be once every three months for most higher quality filters, but we have a rule of thumb that we suggest our customers to go by. If the filter is dirty, change it! A dirty air filter can exacerbate or cause damage to pricey components, like your compressor, so it's better to change it out more often than not. If you want to stick to the manufacturer's recommended limit, we suggest scribbling the date on the filter when you swap it out, and adding a reminder for yourself in your phone or on a calendar. Also note that your filter manufacturer may have a different recommendation from your HVAC system manufacturer.

Figuring out how often to change your air filters relies upon several factors:

Type of filter your A/C system requires
The collective air quality of your San Antonio area home
Pets – Birds, cats, dogs, hamsters (do you have one?), etc.
Occupancy of the home
General air pollution in the San Antonio area or construction taking place nearby

For the common 1"-3" air filters, the OEM specs basically suggest to change them every 30-60 days, which is actually a great rule of thumb. However, generalities may not be suitable for your specific needs. If you have to tolerate light to moderate allergies, you might require an upgraded air filter or change them even more often than OEM specifications. On the other hand, if you're in a low population area, own a less occupied home (like a vacation home) or an area with little auto traffic, replacing your air filters each year may be quite sufficient. Why do pets matter so much? 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 tremendously dirty filters can cause diminished HVAC performance.

In summary:

Infrequently occupied home or single occupant homes without pets or allergies: Change 6-12 months
Average suburban home without pets: Change every 90 days
House with a pet: 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

Here’s an easy way to stay on top of this; 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 wait… there’s more, your email subscription preferences let’s you set a reminder to change your San Antonio area home's air filter every 30, 60, 90, 120 or 365 days, or a specific date of your choice.

How to replace your return air filter

Most of us know how to replace the air filter in their system, but some residences have another filter in the return vent. Whether you have one or not is dependent on which HVAC system you have. Your system is made to handle a maximum amount of pressure in your house, and the more filters you have the fiercer the blower motor works, which can decrease the life of your system if it isn't designed for it. Discovering whether you have a return filter and replacing it is a piece of cake:

Go to your return air vents.
Some covers have screws and some have tabs. Unscrew or pull tabs to take off the wall.
Inspect for a filter. If one is in place, pull it out and record the size.
Verify the filter type is the one recommended by the manufacturer.
If filter is dirty, replace with the manufacturer's recommended filter of the same size and type.

Crazy as it may seem, filters can greatly impact your home's airflow, which is why we recommend checking in with the manufacturer. A more expensive HEPA filter that is designed to catch tinier debris will restrict airflow more than a cheaper filter. With restricted airflow comes more pressure on your system, so you need to verify that your HVAC system was engineered to handle it. Otherwise, you may experience lowered heating and cooling efficiency in your home, and unit parts may wear out much faster than the standard.

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