Change Your Furnace Filter

furnace filterWhether you’re heating or cooling, the filter that removes dirt is the same filter: the one on the side of your furnace. When your furnace filter is dirty, the dirt restricts airflow through your system. Changing your furnace filter keeps the air flowing evenly, reduces stress on your HVAC system and lowers your energy bills.

Check your HVAC filter monthly. How fast it gets dirty depends on the number of people and pets, and amount of dust, in your home. Replace your heating and cooling filter at least every three months, more often if needed.

Time — 5 minutes
Difficulty — Easy
Expertise — None
Frequency — Four times a year



  1. Locate the filter. It’s usually where air enters the furnace, near the fan.
  2. Slide the filter out and note its size, which is printed on the filter. Also find the airflow arrow printed on the filter and note the direction that it points.
  3. Replace the filter with one of the same size, with the airflow arrow pointing in the same direction.


Tips and Warnings

  • Once you know what size filter your heating and cooling system uses, stock up so you have them on hand.
  • Mark the direction of the airflow arrow on the furnace so you can more easily remember the orientation of the filter the next time.
  • If a smoker or someone with allergies lives in the house, consider installing an electronic air filter to take very small particles out of the air.

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      • San Jose, CA

    If you own pets, and your furnace air intake is toward the floor of your home, you will probably be changing your filters MORE OFTEN than the recommended period between "normal" filter changes, suggested by manufacturers.

    We have TWO dogs.

  1. This is definitely an important maintenance task. I try to change my filter regularly on the 1st day of the month. When the first day of the month arrives, I can usually remember that I need to complete that task. During heavy usage of the unit, I sometimes need to change the filter every 2 or 3 weeks.


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