Homeowner guide
Air filters: how often and why
Your air filter protects your equipment as much as your lungs. It's the cheapest maintenance you can do, and the one that prevents the most service calls.
Why it matters
Every bit of air your system heats or cools goes through the filter. When it clogs, airflow drops. That can freeze the AC coil in summer, overheat the furnace in winter, and make the system run longer on every cycle. A clean filter keeps the blower, coil and ductwork cleaner too.
How often to change it
The more people, pets and activity in a home, the faster a filter fills up. Use these as starting points, and check your filter once a month. If it's gray and you can't see light through it, change it.
| Your household | 1-inch filter | 4–5 inch media filter |
|---|---|---|
| One or two people, no pets, no allergies | Every 90 days | Every 6–12 months |
| Typical family | Every 60 days | Every 6 months |
| Pets, several kids, or allergies | Every 30–60 days | Every 3–6 months |
| Smokers, remodeling or construction dust | Every 30 days (check weekly during projects) | Every 3 months |
Change it more often during the peak of summer and winter, when your system runs the most.
MERV ratings explained
MERV (Minimum Efficiency Reporting Value) measures how well a filter catches particles between 0.3 and 10 microns. Higher numbers catch smaller particles.
| MERV | What it catches | Good for |
|---|---|---|
| 1–4 | Large particles: lint, dust mites, pollen, carpet fibers | Basic equipment protection |
| 5–8 | Adds mold spores, pet dander and finer dust | Most homes |
| 9–12 | Adds finer dust and more fine particles | Pets and allergies |
| 13–16 | Very fine particles, including smoke and many bacteria | Allergies, asthma, smoke, if your system can handle it |
The EPA recommends a filter rated at least MERV 13, or as high a rating as your system's fan and filter slot can handle.
Higher isn't always better
A tighter filter can restrict airflow on some systems, especially with 1-inch filter slots. If you move up to MERV 11 or 13 and notice weaker airflow, more noise or ice on the AC coil, go back down a step and ask us. A 4- or 5-inch media filter cabinet lets you run a high-MERV filter without choking the system, and it lasts months longer.
Buying the right one
- The size is printed on the edge of your current filter, like 16x25x1. Buy the same size.
- The arrow on the frame points toward the furnace or air handler, the direction air flows.
- Write the date on the frame when you put it in.