How Often to Change Your Filter

The real answer depends on your filter type, home size, and whether you have pets.

The "Every 90 Days" Rule is Wrong

You have probably heard to change your furnace filter every 90 days. That number comes from filter packaging, not from HVAC engineers. The real answer depends on four things: filter thickness, whether you have pets, how many people live in your home, and local air quality.

Change Frequency by Filter Type

Filter Type	Thickness	No Pets	With Pets	Allergies
Fiberglass	1 inch	30 days	20 days	20 days
Pleated (MERV 8-11)	1 inch	60 to 90 days	30 to 60 days	30 to 45 days
Pleated (MERV 13)	1 inch	60 days	30 days	30 days
Thick Media	4 to 5 inch	6 to 12 months	6 months	6 months

Factors That Speed Up Filter Clogging

Pets: Dog and cat dander is one of the biggest filter-cloggers. Two pets means changing 30 to 50 percent more often.
Multiple people: More activity means more dust, skin particles, and tracked-in debris.
Nearby construction: Outdoor dust infiltration spikes during nearby building work.
Running system continuously: Systems that run all day cycle more air and load filters faster.
High MERV filter: Denser filters catch more particles but fill up faster.

The Visual Check Test

Pull your filter out and hold it up to a light source. If you cannot see light through the filter media, it needs to be replaced regardless of how long it has been installed. A clogged filter forces your blower motor to work harder and can increase energy costs by 5 to 15 percent.

Find Your Replacement Filter