Merv Guide
Filterflow Guide
Which MERV rating is right for your furnace filter?
MERV (Minimum Efficiency Reporting Value) tells you how well a filter captures airborne particles. Higher MERV = more filtration, but also more airflow restriction. Picking the right one depends on what you want to filter and what your HVAC system can handle.
What does MERV mean?
MERV is an industry-standard scale developed by ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers). It rates filters on a 1–16 scale based on their ability to capture particles of different sizes — measured in microns.
Filterflow offers the three MERV ratings most common in residential HVAC: Merv 8, Merv 11, and Merv 13. Anything below Merv 8 (fiberglass throwaway filters) doesn't meaningfully filter air; anything above Merv 13 restricts airflow too much for typical home HVAC.
MERV comparison
| Merv 8 | Merv 11 | Merv 13 | |
|---|---|---|---|
| Captures | Dust, lint, pollen, dust mites | + Pet dander, mold spores, fine dust, auto emissions | + Smoke, bacteria, viral carriers, very fine particulates |
| Particle size | 3.0 – 10 microns | 1.0 – 3.0 microns | 0.3 – 1.0 microns |
| Best for | Standard residential use, budget-friendly | Allergy sufferers, pet owners, families with kids | High-end homes, immunocompromised tenants, wildfire areas |
| Airflow restriction | Lowest | Moderate | Higher — verify HVAC spec |
| MPR equivalent | ~600 | ~1000–1200 | ~1500–1900 |
| FPR equivalent | ~5 | ~7 | ~10 |
MPR (Microparticle Performance Rating) is 3M's proprietary scale. FPR (Filter Performance Rating) is Home Depot's. Both correlate roughly to MERV but aren't standardized industry-wide.
How to choose
Start with Merv 11 if you're not sure
For most rental properties, Merv 11 is the sweet spot. It catches the particulates that matter for indoor air quality (pet dander, fine dust, mold spores) without restricting airflow enough to strain a typical residential HVAC system. It's the rating we recommend by default.
Choose Merv 8 if cost is the priority
Merv 8 is the budget option. It still meaningfully filters air — capturing dust, lint, pollen, and dust mite debris — but doesn't catch the finer particles. If you have tenants with no specific air quality concerns and you're optimizing for cost, Merv 8 is the practical pick.
Choose Merv 13 if your tenants have specific needs
Merv 13 is hospital-grade filtration for residential use. It captures very fine particles including smoke, bacteria, and viral carriers. Best for tenants with allergies, asthma, or immunocompromised conditions — or for properties in wildfire-prone areas where smoke is a recurring issue.
Important: verify your HVAC can handle Merv 13. Higher MERV ratings restrict airflow, which can strain older furnaces or oversized systems. Most furnaces made in the last 15 years can handle Merv 13 without issue, but verify with your HVAC manufacturer's spec sheet before subscribing. Symptoms of an over-restrictive filter: short cycling, longer run times, or unusual sounds from the blower.
Common MERV questions
Is a higher MERV always better?
No. Higher MERV captures more particles but restricts airflow more, which can stress your HVAC system. The "best" MERV is the highest your system can comfortably handle. For most homes, that's Merv 11.
Can I switch MERV ratings between subscription shipments?
Yes. Change the MERV setting in your account, and the next shipment will reflect the new rating. No fee, no commitment.
Will a higher MERV make my heating bills go up?
Marginally, yes. A more restrictive filter forces your HVAC to work slightly harder. The difference is usually small (a few dollars per month at most), but if you're noticing significantly higher bills after switching to Merv 13, your system might be straining and a lower MERV is the right call.
How often should I change my filter?
For 1-inch filters at Merv 8–13, every 30 days is the standard recommendation. Filters that go longer get clogged, which both reduces filtration effectiveness and restricts airflow further (the opposite of what you want). Filterflow ships monthly by default for this reason.
What about Merv 14, 15, or higher?
These ratings exist but are designed for commercial HVAC systems with much higher airflow capacity. Installing them in a residential furnace is almost always a bad idea — the airflow restriction overwhelms typical home systems.
Ready to subscribe?
Pick your filter size, choose your MERV rating, and we'll handle the rest. Subscription delivery, SMS reminders, install confirmation.
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