HEPA vs MERV Filters: What Are the Differences?

Are HEPA filters better than high MERV filters? It depends on the MERV rating. MERV filters in the MERV 17-20 range trap as much dirt and dust as HEPA filters.

But there’s an important distinction – they are different types of filters. In other words, you won’t generally find MERV filters for HEPA applications like an air purifier or vacuum cleaner. The opposite is also true.

This page focuses on HEPA vs MERV filters – their effectiveness and uses specifically for HVAC applications.

HEPA vs MERV Filters Overview

If you are a homeowner, you have probably spent some time trying to learn about your HVAC system. One of the first things that you have probably found out is that regularly changing your HVAC system’s filter is an important part of keeping your home’s airflow clean and pure.

HVAC filters come in different sizes and efficiency levels, and some systems can only handle certain types of filters. This guide will help you understand the differences between HEPA and MERV ratings and discuss the best uses for each type of filter.

Here’s the question underlying much of this research: How well do MERV vs HEPA filters work? Let’s start with a visual before getting deeper into the details. 

MERV Rating

Avg. Arrestance

Particle Size Range

Filter Type

Particles Removed

MERV 4

60-80%

>10.0 microns

Fiberglass Filter

Dust mites, Carpet fibers

MERV 5

20-34%

3.0-10.0 microns

Pleated Filter

Mold spores,  Pollen, Hair spray

MERV 6

35-49%

MERV 7

50-69%

MERV 8

70-85%

MERV 9

>50%

1.0-3.0 microns

Pleated Filter

Pet Dander, Fine Dust

MERV 10

50-64%

MERV 11

65-79%

MERV 12

80-90%

MERV 13

>75%

0.30-1.0 microns

Commercial Filter

Bacteria

MERV 14

75-84%

MERV 15

85-94%

MERV 16

>95%

MERV 17

99.97%

0.30-1.0 microns

HEPA Filter

Virus

MERV 18

99.997%

MERV 19

99.9997%

MERV 20

99.99997%

Particle Sizes

Something that is helpful to know when discussing filtration options is how particles are measured. Particle size is determined using a measuring unit called “microns.” One micron is 1/1,000 millimeter or .0000394 inches. Tiny.

For reference, the width of a human hair is about 100 microns. MERV and HEPA filters are measured by the size of particles they can effectively trap from the air. The more powerful the filter, the smaller sized particles it will filter out of the air that passes through it, and the healthier the air you breathe will be.

Is a More Powerful HVAC Filter Always Better?

Filtration will be better, but a high-MERV filter might do more harm than good.

Yes, it seems intuitive that a more powerful filter is always better because it traps more airborne particles. However, there is actually a downside to powerful HVAC filters – they can damage your HVAC system. The more effective a filter is at trapping particles, the thicker the filter fibers usually are. When the filter itself is dense and fibrous, the HVAC fan has to work much harder to push air through the filter. This uses up extra energy and can wear out your air blower much faster. It can also cause airflow restriction which creates hot and cold spots throughout your home. The worst-case scenario is that the system working too hard can cause irreparable damage like a cracked furnace heat exchanger (which might also leak deadly carbon monoxide) or a failed AC or heat pump compressor.

Your goal when searching for the right HVAC filter should be to find the “sweet spot” – a filter with effective particle removal that is appropriate for your HVAC system.

With that goal in mind, let’s discuss MERV filters and HEPA filters.

MERV Air Filters

This content covers the same basic types of information about these two common filters – MERV vs HEPA.

What is a MERV Rating?

HVAC filters are differentiated by their MERV rating. MERV stands for “Minimum Efficiency Reporting Value.” MERV rating is a measurement of how effective a filter is at removing materials from the airflow that passes through it. The higher the MERV rating, the more particles will be trapped by the filter. Higher MERV ratings can also trap smaller particles – more and smaller, both of which are important to indoor air quality (IAQ). The most popular MERV rating for residential homes is MERV 8. It hits the sweet spot between high-quality filtration and energy efficiency! But for homes with higher filtration needs, a MERV 11 or even MERV 13 filter might be best and probably won’t damage your equipment.

How Do I Know Which MERV Rating to Get?

Don’t be intimidated by MERV ratings! Finding the right MERV rating for your home’s HVAC system is something any homeowner can do. Follow this three-step process to determine your filtration needs and find the best MERV rating for you: 

  1. Check the documentation for your HVAC system – Every HVAC system has a certain filtration capacity. Your HVAC system’s documentation will tell you what the maximum MERV rating is that your system can handle. For most residential homes, a MERV rating of 13 is the maximum rating that the system can handle.
  2. Assess your home’s particular needs – Once you know the maximum MERV rating that your HVAC system can handle, you can move onto assessing your home’s particular filtration needs to find the best rating within that range. Do you have furry pets? Do you live in an arid, dusty climate? These are the types of questions to consider as you assess your home’s filtration needs. The more dust and fur in your home, the better filtration you will want.
  3. Consider your household’s health – Are there household members with asthma, allergies, or other respiratory illness? If there are, you may be a good candidate for a more powerful HVAC filter.

There is a lot more information of this type in the Pick HVAC Guide called Recommended MERV Ratings.

HEPA Air Filters

True HEPA Filtration for AC350 Air Purifier

These filters do a great job removing small particles. As we said, they are the equivalent of MERV 17-20 filters, which are typically only used in medical settings or places where a dust-free environment is necessary.

What is a HEPA Filter?

HEPA stands for “High Efficiency Particulate Air.” Sometimes it is written as “High Efficiency Particulate Air [Filter],” most notably in the United States Department of Energy’s definition.

HEPA filters offer some of the most powerful filtration available on the market. To help you learn about HEPA filters, we have compiled a list of the most important information about them and their uses, including information about HEPA's effectiveness against Covid-19.

What size particles do HEPA filters trap?

HEPA filters can trap particles as small as 0.01 microns. But the real superpower of HEPA filters is their ability to effectively capture particles sized 0.3 microns. Why is this so impressive? Because particles sized 0.3 microns are known as the MPPs. This stands for “Most Penetrating Particle Size.” Experts have learned that particles of this size are the hardest to trap in a filter. Even much smaller particles are easier for a filter to trap than 0.3 micron-sized particles – sounds fishy to us, but that’s what the EPA says. This is why HEPA filters are known for their ability to trap those pesky MPPs.

Info tip: Microns are often represented by their scientific symbol µm.

How effective are HEPA filters?

HEPA effective

HEPA filters trap and remove 99.97% of airborne particles sized 0.3 microns or an even higher percentage for smaller or bigger particles.

Are HEPA filters effective against Covid-19?

We are all too familiar with the Covid-19 virus. After more than a year of hand-washing and extra safety precautions, you’ve probably become aware of something called an N95 mask, or KN95 mask. Experts have recommended N95 masks as the most effective mask at preventing the spread of Covid-19. An N95 mask is effective at filtering out 95% of particles sized 0.3 microns.

How does a HEPA filter compare with an N95 mask? A HEPA filter is more effective, filtering out 99.97% of airborne particles sized 0.3 microns. Covid-19 is estimated to be about 0.1 microns in size, which puts it right in the sweet-spot for HEPA’s filtration abilities. Remember, 0.3 microns is the hardest particle size to trap, so a HEPA filter’s ability to trap particles sized 0.1 microns (like Covid-19) is even higher than 99.97%. That’s pretty impressive!

To prevent the spread of Covid-19 through a forced-air HVAC system, scientists recommend using a filter rated MERV 13 or higher. HEPA filters are the equivalent of a minimum of MERV 17 rating.

Where do HEPA filters work best?

HEPA filters were originally created specifically for laboratory and factory use, but now they are used more widely. HEPA filters are particularly common in surgical areas or isolation rooms containing patients with infectious diseases.

During the Covid-19 pandemic, HEPA filters have been widely used and recommended in care rooms for Covid-19 patients.

And as we said, vacuum cleaners and home air purifiers often use HEPA filters.

There are no true HEPA filters made for a home’s furnace or air handler. HEPA filters are a MERV 17 to MERV 20 equivalent, which restricts airflow too much for a typical HVAC system. A standard HVAC system has a 1-inch filter, while MERV 17-20 filters are between 5 and 8 inches in width.

You can get a HEPA-like filter with a MERV equivalence of 13-16, which will offer excellent HEPA-like filtration. The highest MERV rating available in a standard 1-inch filter is MERV 14. If you want a filtration level that is closer to true HEPA, such as MERV 16, you need to upgrade your HVAC system to handle a 4 or 5-inch filter. This means having the furnace cabinet or the return air trunk or plenum modified to accommodate the thicker filter. This tends to be expensive, in the range of $300 to $600+, and still doesn’t offer true HEPA filtration.

What if I want a true HEPA filter but my home’s HVAC system can’t handle it?

Most home HVAC systems are not designed for a HEPA filter. If you can’t do HEPA, a MERV 13-16 filter is the next best thing and will still offer superior filtration. But we do not recommend using a filter above MERV 13 for your furnace or air handler. The entire HVAC industry agrees. Our guide called When You Shouldn’t Use a High MERV Filter is “must” reading before you slap one of them into your system.

HEPA Alternatives to High MERV Filters

If you have your heart set on a true HEPA filter, there are options for you!

If your HVAC system can’t handle a HEPA filter, consider getting a portable HEPA air purifier instead. A stand-alone HEPA air purifier, also known as a portable HEPA air cleaner, will provide high-powered filtration to your home without damaging your HVAC system.

Portable HEPA air purifiers vary in price, depending on the size of the machine. They can range in price from about $60.00 to $600.00 or more. HEPA air purifiers can be purchased online and at most big box stores like Home Depot or Lowes. For more information on HEPA air purifiers and our top recommended brands, check out our page Best HEPA Air Purifiers Reviews and Buying Guide 2021.

And if Covid is a particular concern in your home, see our post on UV Germicidal Lights for HVAC Systems.

Summary

We hope that this guide on HEPA vs. MERV has given you a deeper understanding of filtration options that are available for you. We always recommend that homeowners consult an HVAC specialist before making any major changes to their home HVAC systems. HVAC specialists can also help you to determine what is the best filter option for you!

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