The Only Furnace Filter Changing Guide You’ll Ever Need

Why Should I Change the Furnace Filter?

Simply, changing your furnace filter is the most important thing you can do to keep your heat working at top efficiency, and it’s so easy that a 10 year old could do it.

(Not that we’re recommending this. Don’t make your 10 year-old change your furnace filter.)

Your furnace functions by sucking up the cold air from your house, heating it, and then pushing it back out. In other words, the entire functioning of your indoor heat is based on your furnace’s ability to move air around. If the furnace has to suck air through a blocked filter, you can imagine how much harder this process will be and how much less effective your furnace will run as a result.

Looking for info on changing your AC filter? Don’t sweat! In most cases, this is the same filter as your furnace filter, so the information is the same, but we created a separate guide here for all the info you need.

“Low investment, high returns, baby!”

What Happens If I Don’t Change My Furnace Filter?

Not changing your furnace filter will lead to a buildup of dust, dirt, pet hair, and any number of other gross debris in your filter. It will taint the air quality, make your heating irregular in your house, and ultimately, break your furnace. There is also a small chance that not changing your filter will eventually lead to a fire or CO2 leak. Don’t make your furnace work harder than it has to–change your filter!

Click here to read more about important tasks toward properly winterizing your home. We also have helpful information on the real costs of home ownership as well as the top maintenance tasks for your home.


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  • 1. Turn Off Furnace
    • This is the key to keeping yourself safe as you change the filter. If you don’t know how to turn off your furnace, you can just turn the fuse off that controls the furnace in the circuit breaker. If you do this, you might need a flashlight to change the filter, since the surrounding lights might also be disconnected when you turn off the fuse.

      Next Step
  • 2. Locate the Filter
    • Locating your furnace filter can be a little tricky if you don’t already know where it is. It should either be in the return air vent, which will be a large vent located somewhere in your home, or it will actually be inside of your furnace behind some metal casing.

      (Quick note: If it is in the return vent, chances are this is the same filter that your AC unit uses.)

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  • 3. Find Correct Replacement Filter
    • Before you change your filter, you’ll have to purchase a new one at a hardware store. Make sure you buy the correct size and type of replacement filter by looking at what filter is already in your system. (There is also an option to buy a reusable filter so that you don’t have to constantly replace the filter, but there are mixed reviews on whether or not these reusable filters really work as well.)

      Next Step
  • 4. Remove Old Filter
    • If your filter is located behind the return air vent, open the vent (you might need a screwdriver) to take out the old filter. If your filter is located in your furnace, remove the casing, using your flashlight if necessary, and take the filter out.

      Next Step
  • 5. Insert New Filter
    • Insert the new filter being sure to look at the arrows on the filter and in the frame of the filter that signifies which direction to put the filter in. Putting it in the wrong way can significantly impact the efficiency of the filter.

      Next Step
  • 6. Turn Furnace Back On
    • Once the filter is securely in place, put the vent or casing back on and turn the power on. Voila! Pet hair has got nothing on you, pal.

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