Is a MERV 13 Filter Upgrade Worth It? When Yes, When No

What MERV 13 gains you

Minimum average capture from EPA's "What is a MERV rating?"

Particle size	MERV 8	MERV 11	MERV 13
0.3 to 1 µm	No minimum	20%	50%
1 to 3 µm	20%	65%	85%
3 to 10 µm	70%	85%	90%

The gain is concentrated in fine particles: smoke from wildfires, wood stoves and cooking, and fine dust. EPA's guidance on respiratory viruses also suggests MERV 13 or the highest the system can handle, while noting that air cleaning alone is not enough to protect people. See do air purifiers help with viruses?

When it is worth it

• Your home has forced-air heating or central air that runs regularly.
• Wildfire smoke, traffic or a wood stove raises indoor particles.
• Someone in the home has allergies or asthma.
• Your system handles it without the warning signs below.

When it is not, or not on its own

Your system cannot handle the resistance

EPA's technical summary says not all HVAC fans can accommodate high-efficiency filters without reducing airflow to the point where heating or cooling capacity is lost, which can cause comfort problems and increase the risk of component failure. Warning signs after an upgrade:

• Noticeably weaker airflow from registers.
• Whistling at the filter slot or return grille.
• Rooms that no longer reach the thermostat setting.
• A filter bowing or pulling out of its frame.

EPA suggests consulting an HVAC technician to be certain a filter will work, and says performance should be measured by a professional in existing homes. Ask for a static pressure reading with the new filter.

The fan rarely runs

EPA says furnace filters work only while the system is operating, and that systems usually run less than 25% of the time during heating and cooling seasons; in mild weather, or with window air conditioners, they may not run for months. Running the fan longer filters more air, but EPA says longer run times increase electricity costs and may reduce humidity control in the cooling season.

Ways to get MERV 13 without the airflow penalty

1. Choose a low-resistance MERV 13. EPA's technical summary notes that extensive pleating and electrostatically charged media can deliver high MERV with low resistance. Filtrete claims its MPR 1900 (MERV 13) has the highest airflow of any brand's residential 1-inch retail MERV 13, based on California Energy Commission data; we have not verified that claim.
2. Go thicker. A 4 or 5-inch media cabinet reaches MERV 13 with more media and less resistance. See the best whole-house air filters.
3. Fix the fit. EPA says filters should fit snugly and that bypass airflow around poorly fitted frames significantly decreases effectiveness, so a well-fitted MERV 11 can outperform a gapped MERV 13.
4. Add a portable purifier. For the rooms that matter most, a HEPA purifier sized by its smoke CADR runs continuously. See the best air purifiers.

The cost

A MERV 13 filter usually costs more than a MERV 8 of the same size, and it may need changing a little more often in dusty homes because it catches more. EPA says makers typically suggest replacement every 60 to 90 days; Filtrete says at least every 90 days for its MERV 13. The larger cost is running the fan longer, if you choose to; EPA notes that longer run times raise electricity costs.

Our verdict

Try MERV 13 if your home has a forced-air system that runs regularly. Watch for the warning signs for a week or two; if you see them, step down to MERV 11 or ask a technician about a media cabinet. For a comparison of the levels, see MERV 8 vs 11 vs 13, and for picks, the best HVAC filters.