How Often Should I Change My HVAC System Filter?
There’s no one-size-fits all answer to the question of when and how often you should change your heating and air filters. That’s because everyone uses their system differently, and HVAC filters only need to be changed when they’re too full of filtered matter to continue functioning efficiently. If you run your system all day, every day in the summer but only turn it on occasionally in the winter, you’ll probably need to change your filter much more frequently in the summer than you do in the winter. If you run your system only on rare days when temperatures are extreme in your area, you may not need to change your filter more than once or twice a year.
But there’s more to it than just how often you run your system. Filter load also depends on what goes on in your house and how large the space the filter covers is. If you have a single-zone system for a three-story house with lots of pets and people, including people who smoke indoors, your filter is likely to need frequent changes.
Because there’s no quick answer, you’ll need to check your filter periodically, particularly when the system is in heavy use. Once a month should be sufficient even if you use your system a lot, but if your once-monthly check always yields a completely filthy filter, bump your check up to bimonthly or even weekly.
When to Change the Filter
So what are you looking for when you check? You want to see a filter that’s in good repair – no cracks, tears, or anything like that. If it seems clogged with hair, dust, and debris, then it is time to place the HVAC air filters. When in doubt, it doesn’t hurt to change the filter; a clogged filter doesn’t work as efficiently, and it can also slow down your entire system.
Finally, your filter should be dry and free from mold. If you notice any fungus growth or dampness in your filter, not only should you immediately change it, you should call an HVAC service technician to ensure your system's effectiveness.
How to Change the Filter
If your HVAC unit comes with an instruction manual, do some research to make sure you know exactly what kind of filter you need and how it should fit into the unit. Some filters have a front side and a back side that should face toward or away from the direction of airflow in your unit, and if you’re not sure which way the filter should face, it’s important to look it up to so you install it properly.
Different systems also have different specific installation instructions, but there are some general rules to keep in mind while replacing HVAC filters:
Turn the system off before you do anything that requires you to reach into the mechanisms or housing
The filter should fit into the system snugly with no gaps or bending. A too-small or too-large filter can cause problems down the road and lead to less-efficient operation
Clean up any debris that falls from the dirty filter before you install the new one and turn the system back on
Restart the system to ensure everything’s working properly before you close it up and walk away
You can also start a log noting when you’ve replaced your filter so you can make a more informed decision on whether it’s time to change it. Most systems take disposable filters, but if you’d rather clean your filter and replace it, you can buy a kit to make a reusable filter for your system.