Quick answer
Every 1 to 3 months for a standard 1-inch filter — every month if you have pets, allergies, or the system runs all day in peak summer. Thicker 4–5 inch media filters can last 6 to 12 months. When in doubt, hold it up to the light.
Why the filter matters
The filter keeps dust out of the system — and the system needs air flowing through it to cool. A clogged filter makes the blower work harder, cuts cooling, raises your bill, and can even freeze the indoor coil.
How often, by situation
- Standard 1-inch filter: every 1–3 months
- Pets or allergies at home: every month
- Peak summer, running all day: check it monthly
- 4–5 inch media filter: every 6–12 months
- Light use or a vacation home: every 6 months
How to check it
Slide it out and hold it up to a light. If you can't see light through it, it's time. A gray, matted surface means it's overdue.
Picking the right filter
Match the size printed on the frame of the old filter. Most homes do well with a MERV 8 to 11 filter. Higher-MERV filters catch more, but they can restrict airflow on systems that weren't designed for them — ask us before going above MERV 13.
Putting it in the right way
Every filter has an arrow on the frame. It points toward the system, in the direction the air flows — away from the return grille.
When to call a pro
- The filter clogs again within a couple of weeks
- There's dust or mold around the filter slot
- Airflow is weak even with a clean filter
- You're not sure which size or type your system takes