Air filter shopping is needlessly confusing. Walk down the filter aisle and you'll see MERV numbers, MPR numbers, FPR numbers, brand names, and claims about removing 99% of various things. Here's the version that actually matters.
What MERV measures:
MERV stands for Minimum Efficiency Reporting Value. It rates a filter's ability to capture particles of various sizes, from 1 to 16. Higher MERV catches smaller particles.
- MERV 1 to 4: Catches large stuff like lint and visible dust. These are the cheap fiberglass panels. They protect your AC equipment but do almost nothing for indoor air quality. - MERV 5 to 8: Catches pollen, mold spores, pet dander. This is the sweet spot for most homes. - MERV 9 to 11: Catches fine dust, smoke particles, smaller allergens. Good for homes with allergies or pets. - MERV 13: Catches bacteria, smoke, virus carriers. Often advertised post-COVID. Requires more powerful airflow than many residential systems can provide. - MERV 14 to 16: Hospital-grade. Requires commercial HVAC equipment.
The trade-off nobody mentions:
Higher MERV filters are denser. Denser means more resistance to airflow. More resistance means your AC blower has to work harder, your system runs longer, and over time you can damage the blower motor or burn out the system early.
This is why MERV 13 isn't automatically better. Most residential AC systems were designed for MERV 8 to 11. Drop in a MERV 13 and you may save on Amazon delivery while costing yourself a blower motor.
The honest recommendation for a typical Brevard County home:
- MERV 8 to 11: the right answer for most homes. Catches the stuff that matters (pollen, dander, mold spores, fine dust) without choking your system. - MERV 13: only if someone in the home has serious respiratory issues AND your AC is sized to handle it. Have an HVAC contractor confirm before you switch. - MERV 4 or below: only if cost is the only thing you care about. You're getting essentially no filtration of what's in your air.
How often to change it:
- Florida humid season (May to October): every 30 to 60 days - Drier months: every 90 days - With pets: shorten the above by half - After hurricane or major construction: check after one week
MPR and FPR vs. MERV:
3M's MPR and Home Depot's FPR are private rating systems. They roughly correlate to MERV like this:
- MPR 600 to 1500 ≈ MERV 8 to 11 - MPR 1900 to 2200 ≈ MERV 12 to 13 - FPR 5 to 7 ≈ MERV 8 to 11 - FPR 10 ≈ MERV 13
If you're comparing across brands, MERV is the more universal standard. Stick with MERV ratings and you'll never go wrong.
One last thing: the most expensive filter on the shelf that you change late is worse than a basic MERV 8 you change on time. Whatever you buy, set a reminder.