Changing your furnace filter is one of the simplest and cheapest ways to protect your HVAC system and your home's air quality. It takes most homeowners under five minutes once they know where to look, and you don't need any tools.
Why it matters
A clogged filter forces your furnace to work harder to push air through the house, which drives up your energy bill and shortens the life of the system. It also lets more dust, pet dander, and other particles circulate through your home instead of getting trapped. Staying on top of filter changes is one of the easiest ways to avoid an expensive repair call down the line.
How often to change it
How often you need a new filter depends on the type you use and what's going on in your home:
- Basic fiberglass filters (1 inch): every 30 days
- Pleated filters (1 inch): every 30 to 90 days, depending on usage
- Thicker media filters (4 inch): every 6 to 12 months
Change filters more often, closer to every 30 days, if you have pets, smoke indoors, burn candles or a wood-burning fireplace regularly, live near construction, or have a household member with allergies or asthma. When in doubt, check the filter visually once a month and replace it when it looks gray or coated in dust.
What you'll need
Just a replacement filter in the correct size. Your current filter's size is printed along its cardboard edge, look for a set of three numbers such as 16x25x1. If you want better filtration for allergies or pet dander, look for a filter with a MERV rating between 12 and 16, just confirm your furnace can handle a higher-MERV filter without restricting airflow, check your owner's manual if you're not sure.
Step-by-step instructions
- Turn off your furnace at the thermostat or the system switch. This isn't strictly required, but it's a good habit and keeps dust from blowing around while the filter is out.
- Locate the filter. It's usually either in a slot on the furnace itself or behind a return-air vent grille somewhere in the house. If it's behind a grille, you may need to loosen a few screws or unclip a cover to get to it.
- Slide out the old filter. Note the direction of the small arrow printed on its frame before you set it aside.
- Dispose of the old filter in a regular trash bag. It can get dusty, so have the bag ready before you pull it.
- Slide in the new filter with the arrow pointing in the same direction as the old one, toward the furnace or blower, in the direction the air flows.
- Turn your furnace back on and set a reminder for your next change based on the filter type you're using.
Signs you're overdue
- Furniture and surfaces collect dust noticeably faster than usual
- The furnace runs longer or more often to reach the temperature you've set
- The filter itself looks gray and matted instead of white or off-white
- Your energy bill creeps up without an obvious explanation
If you've just moved into a new place and aren't sure where your furnace or filter even is, that's a common question from new homeowners, and we're always happy to help point you in the right direction.
