Best 20x25x4 Air Filter

20x25x4 furnace filters are designed to help maintain your Indoor Air Quality very high. These exceptionally thick furnace filters have higher surface areas than their thinner counterparts.

They can take in large amounts of contaminants to keep the air in your home clean. In this review, we look at some of the best 20x25x4 furnace filters.

We also advise you on what to look out for when purchasing the best 20x25x4 furnace filters.

Why does my Furnace Filter get Dirty so Fast?

Your furnace filter may be getting dirty so fast because of various reasons. Remember that furnace filters are designed to get dirty after some time. They trap all manner of contaminants, including dust, mites, and smoke particles. After some time, your filter’s surface is so full of contaminants that it cannot take up more. This is the right time to replace it.

The rate at which your furnace filter becomes dirty varies with the seasons and your house’s actual conditions. When the air is filthy, your furnace filter will become dirty sooner than later.

During the off-peak season, your furnace filter will not accumulate a lot of dirt particles. Therefore, it will remain relatively clean for a longer time than used during the peak seasons.

Therefore, your furnace filter may be getting dirty fast because the air in your home is very contaminated. The high level of contamination maybe because of the prevailing weather conditions or the presence of many dirt sources.

Such sources include smoke, dust, and mites. In other words, your furnace filter will be overworking to keep the Indoor Air Quality high enough for you to stay in the house comfortably.

How Often should 20x25x4 Furnace Filters be Replaced?

The best time to replace your furnace filter is when the period indicated on the pack expires. Manufacturers of furnace filters indicate the period when they believe their devices will be helpful to you. The time varies considerably.

However, most brands of furnace filters are designed to last for three months. This means that you need to uninstall the first piece and install the replacement one after three months. Some furnace filters are designed to last for six months. If such brands come in packs that contain two pieces, then a pack can last for a year.

However, the actual period that a furnace filter remains useful depends on the prevailing conditions. If you use your furnace filter when the house is quite dirty, it will be necessary to replace it earlier than the time that is indicated on its packaging.

To tell when it is the right time to replace your furnace filter, you can either assess the quality of the air in your home or perform a simple test.

The test entails using a clean sheet of white paper and keeping it near your house’s vents for about 30 minutes. If the paper turns black with soot and other contaminants, it is time to replace your furnace filter.

1-Inch vs. 2-Inch vs. 4-Inch Furnace Filters

Many people get lost when choosing the right type of furnace filter. There are 1-inch, 2-inch, and 4-inch types of air filters. The inches indicate the depth of the filters. A rule of thumb is that the thicker the furnace filter, the better in terms of performance.

However, there are many exceptions to this rule. Therefore, you need to understand the pros and cons of having any of the three types of furnace filters.

You will have to replace your thin furnace filter more often than a thick one in terms of the frequency of replacement. A 4-inch furnace filter has a higher surface area than a 1-inch and a 2-inch one. Your 4-inch furnace filter will last for a long time because it will have enough space to capture many contaminants. In other words, it will take a long time before the filter becomes fully saturated.

There is not much difference in terms of performance between these types of filters. The performance of a filter is a function of its MERV rating and not thickness.  Your 1-inch or 2-inch or 4-inch furnace filter will perform poorly if it is of a relatively low MERV rating.

Also, regardless of the thickness, any furnace filter with a high MERV rating will perform well by attracting and trapping even as much as 97% of airborne contaminants.

Are 4-Inch Furnace Filters Good for your HVAC?

4-inch furnace filters are suitable for your HVAC system. Most HVAC systems are designed for such thick furnace filters. Alternatively, you retrofit such a thick furnace filter. The main reason for using a 4-inch furnace filter in your HVAC system is functional.

A 4-inch furnace filter takes longer to clog than a 1-inch or 2-inch furnace filter. A 4-inch furnace filter has a more extensive surface area than a 2-inch or 1-inch furnace filter.

It can accommodate a lot of contaminants before it reaches its capacity. This makes things very easy for you. You do not have to replace your 4-inch furnace filter repeatedly. You may forget about doing this for as long as three months. If you have a thin furnace filter, you will need to replace it quite frequently.

How Long do 20x25x4 Filters Last?

20x25x4 furnace filters may last from three months to six months. This is usually the estimated time that it takes for the filter to be full of contaminants. However, this period may vary depending on the prevailing air conditions. If the air in your home is particularly contaminated, your furnace filter will last for a short period because it will take in all the contaminants quite fast.

Also, high-quality furnace filters tend to last longer than low-quality ones. It is because your high-quality furnace filter has advanced features that enable it to take in more contaminants than a low-quality one.

How to Choose the Best Furnace Filters

Choosing the best furnace filter for your HVAC system can be a tedious task if you do not understand the furnace filters’ basics. There are a few important things that you should look out for when purchasing a furnace filter.

MERV Rating

The MERV rating indicates the number of contaminants that a furnace filter can effectively attract and trap. The higher the MERV rating, the more significant the percentage of contaminants that your furnace filter will trap. Go for furnace filters that have high MERV ratings of more than 12. Such furnace filters can trap up to 97% of all types of contaminants in the house.


The thickness of your furnace filter determines how long it can last. Furnace filters that are 4-inch thick last longer than their thinner counterparts. Go for such furnace filters because they will keep the air in your house clean for a long time before they need to be replaced.

The Surface of the Filter

The best furnace filters are those that have pleated surfaces. The pleating of the strands that form the surface of a furnace filter dramatically increases the surface area. Such furnace filters can trap many contaminants. They hardly allow even the tiniest type of contaminants to seep through and lower the Indoor Air Quality of your home.

Electrostatically Charged Surfaces

Some furnace filters have their surfaces electrostatically charged. The use of electrostatic charge increases the ability of the furnace filters to trap contaminants. Such furnace filters attract small particles that form allergens in the air. Thus, they effectively attract and trapping mites, dust, pollen, and other minuscule particles.

Best 20x25x4 Air Filter – Reviews

1. Nordic Pure 20x25x4 Furnace Air Filter

Nordic Pure 20x25x4 (19_1/2 x 24_1/2 x 3_5/8)...
  • Nominal Size: 20 x 25 x 4, Actual Size: 19 1/2 x 24 1/2 x 3 5/8 (19.5 x 24.5 x 3.63)
  • Measure your air filter for the exact size and compare it to our actual size to ensure proper fit.
  • If you are replacing a Honeywell or Lennox 20x25x4 or an air filter with an MPR rating with an actual depth of 4 3/8, please see our 20x25x5 (4 3/8 actual depth)
  • Nordic Pure MERV 12 is equivalent to MPR 1500-1900
  • Made in the USA

The Nordic Pure 20x25x4 Furnace Air Filter is one of the best furnace filters that you can rely on to deal with all kinds of contaminants in your house.

It has various features that enable it to capture up to 90% of all the kinds of allergens that can be found in your house, including small fur particles from your pets and odor-causing particulates.

With a MERV rating of 12, this furnace filter captures about 90% of contaminants that measure from 0.3 to 1 micron wide. Thus, the furnace filter will do an excellent job of keeping the air in your house clean and maintaining your blower.

It has a surface that is made up of pleated strands. The pleating of the strands increases the overall surface area. This ensures that nearly all the particles that come into contact with the surface area are eventually trapped.

Furthermore, the surface has a charge that automatically attracts contaminants, including dust particles, allergens, and odors.


  • It has pleated strands for effective performance
  • The high MERV rating of 12 enables the filter to trap a high percentage of contaminants
  • It attracts allergens and other contaminants to its surface


  • There are two pieces only in a pack

2. Filtrete NDP03-4IN-2P-2 AC Furnace Air Filter

Filtrete 20x25x4, AC Furnace Air Filter, MPR 1550...
  • OUTPERFORMS FIBERGLASS, WASHABLE AND NON-ELECTROSTATIC 3-month pleated 1 in. home air filters for your furnace, air conditioner or HVAC system
  • DESIGNED WITH EXCLUSIVE Filtrete Brand 3-in-1 technology from 3M to trap unwanted air particles while letting cleaner air flow through
  • ATTRACTS AND CAPTURES microscopic particles such as smoke, cough and sneeze debris, bacteria and viruses - and large particles, including lint, household dust and pollen
  • 1550 MPR has a rating of MERV 12
  • The higher the MPR, the more microparticles - such as pollen, pet dander, smoke, bacteria and viruses - your filter will capture from the air passing through it
  • 54% SMALL PARTICLE CAPTURE, like bacteria and particles that carry viruses ( % captured is based on ASHRAE 52.2 testing for 0.3 to 1 micron particles from the air passing through the filter, which relates to HVAC industry standard efficiency testing)
  • CERTIFIED as asthma & allergy friendly (As outlined in report ASCR: 1246-01)
  • FIND YOUR SIZE: 1550 MPR available in 4 in. , 4 in. slim fit and 5 in. thick air filters
  • FOR OPTIMAL PERFORMANCE of your heating & cooling system or HVAC system, change your home air filter at least every 90 days for 1in. filters, and at least every 12 months for 4in. and 5in. Filters
  • A dirty filter will slow down air flow and make the system work harder to keep you warm or cool - wasting energy. Sign-up for a filter change reminder program that works for you!

The Filtrete NDP03-4IN-2P-2 has some of the most impressive features you would expect to find in such a furnace filter. Primarily, it is made using the exclusive filtration technology developed by the manufacturer. You may find the Filtrete brand a great companion for maintaining high Indoor Air Quality.

Additionally, this furnace filter effectively attracts and traps microscopic substances that are usually found in indoor environments. When you install this furnace filter, you will automatically say goodbye to problems caused by allergens, viruses, and other microorganisms that are usually found in the air.

However, remember that this furnace filter is designed to offer essential protection against such airborne microbes in a home and not a commercial environment.

The only notable drawback of using this furnace filter is that you will have to purchase a replacement pack quite often. There are only two pieces of furnace filters in every pack.

Besides, they are supposed to last for only three months. This means that you will have to purchase a new pack within six months.


  • Excellent performance because of the exclusive Filtrete technology
  • Ideal for creating an immaculate indoor environment
  • High 1150 MPR and 12 MERV ratings


  • There are two pieces in the pack.

3. Honeywell Home 4-Inch-High Efficiency Air Cleaner Filter

Honeywell Home 4-Inch High Efficiency Air Cleaner...
  • A HEALTHIER HOUSEHOLD - Breathe easy in your home with a Honeywell Home 4-Inch High Efficiency Air Cleaner Filter that helps keep hazardous airborne particles out and fresh air flowing in
  • MERV 8 RATING - Get exceptional protection against dust, viruses, bacteria, fungus, pollen, and spores. 20x more effective than than typical 1-inch fiberglass filters
  • RECOMMENDED USE - Recommended for homes with pets, people with allergies, homes with smokers, or anyone wanting cleaner air
  • LONG LASTING FILTRATION - Lasts up to 12 months without losing quality over time
  • EASY INSTALLATION - Honeywell Home's easy-to-install air filters make changing out your air filtration unit quick, painless, and mess-free
  • COMPATIBLE AND CONVENIENT - Compatible with Aprilaire and Space-Gard models 2200 and 2251 and Trion Air Bear 20 x 24 air cleaners
  • DIMENSIONS - Nominal size) 20 x 25 x 4 inches / Actual Size) 18.838 x 24.875 x 4.375 inches

The Honeywell Home 4-Inch-High Efficiency Air Cleaner Filter has an electrostatically charged surface. The charge on its strands attracts small contaminants that also carry a charge.

As a result, this furnace filter is exceptionally effective in trapping all the contaminants that are usually found floating around the air in homes, including dust and smoke particles.

Another important feature of this furnace filter relates to its installation. As you would expect, you do not need to possess new skills to install and maintain a furnace filter.

Just ensure that the lines drawn on its surface are correctly aligned with the airflow direction in your system. You do not need to do anything to keep the furnace filter functioning apart from replacing it when it loses its functionality.

However, you may find the 12 MERV rating of this furnace filter relatively low. There are many brands of furnace filters that have exceptionally high MERV ratings of even up to 14.

However, if you are not keen on getting a furnace filter with a very high MERV rating, this may get the job done and keep your indoor environment clean.


  • Electrostatically charged surface for attracting contaminants
  • It provides long-lasting filtration for about 12 months.
  • Easy installation and maintenance


  • The MERV rating of 8 is relatively low.

4. Aerostar Allergen & Pet Dander 20x25x4 Furnace Filter

Aerostar 20x25x4 MERV 13 Pleated Air Filter, AC...
  • Nominal Size: 20x25x4; Actual Size: 19 1/2" x 24 1/2" x 3 3/4"
  • Comparable to MPR 1500 to 1900 Ultimate Allergen Defense and Honeywell Allergen Elite FPR 10
  • Designed to filter microscopic particles such as lint, dust mites, spores, pollen, pet dander, fine dust, smoke, and bacteria.
  • Simple to install and a cost-effective step towards a healthier home environment. For best results, change your filters every 60 to 90 days but increase frequency to 30 days during peak summer and winter months
  • 100% synthetic electrostatic media for high efficiency with low air flow resistance

If you are looking for a furnace filter with a surface made from synthetic materials, can capture all types of contaminants and is easy to install, consider using the Aerostar Allergen & Pet Dander 20x25x4 Furnace Filter.

The use of 100% synthetic material is quite beneficial because it ensures that the furnace filter captures allergens and other contaminants.

Allergens can trigger severe allergic reactions in some people. Things may be terrible if children are affected. You need a good furnace filter to attract and trap all small particles that may act as allergens to some people.

This furnace filter has a pleated surface and a high MERV rating of 12. These features are critical for any furnace filter that effectively traps allergens. Therefore, using this furnace filter can successfully keep you safe from all types of allergens.


  • It is made of 100% synthetic material that is electrostatically charged.
  • The surface of the furnace filter is pleated to maximize the surface area.
  • Designed for attracting and trapping all types of allergens


  • The furnace filter does not last for a long time during peak times.

5. Green Label HVAC Air Filter

Green Label Brand HVAC Air Filter 20x25x4, AC...
  • Filter dimensions: 19.625” x 24.625” x 3.75”; 498 x 625 x 96 mm
  • MERV 16. Electrostatically charged filter. Lasts up to 12 months
  • Can be used in your home or office, as well as at a hospital laboratory, and any other space where well filtered air is needed
  • Package contains: 2 x HVAC Air Filters 20 x 25 x 4
  • High quality. Customer support. No questions asked return policy. Fully refundable

If you are looking for a furnace filter with a very high MERV rating, the Green Label HVAC Air Filter may be the right choice for you. This furnace filter is rated 16 under the MERV system.

A high MERV rating means that your filter will remove a significant percentage of all airborne contaminants in your house. Furnace filters that have MERV ratings of about 16 can trap 97% of all the contaminants that may be floating around in your home. Therefore, installing the Green Label HVAC Air Filter in your system will keep the Indoor Air Quality very high.

This furnace filter lasts for about six months. This is a significant advantage because you will not have to replace it often. However, the actual time that your furnace filter remains useful depends on the conditions in your home.

During peak times, a furnace filter may last for even just a month. You must occasionally check its status to determine whether it is time to replace it.


  • High MERV rating of 16
  • Long-lasting filtration performance
  • The surface is charged to attract all contaminants.


  • A pack contains two pieces only.

6. FilterBuy 20x25x4 MERV 8 Pleated AC Furnace Air Filter

Filterbuy 20x25x4 Air Filter MERV 8 Dust Defense...
  • 20x25x4 replacement air filters for your furnace, air conditioner, heat pump, or HVAC system (actual size: 19.38" x 24.38" x 3.63")
  • MERV 8 synthetic media (comparable with MPR 600 & FPR 5) protects homes from dust, pollen, and more by trapping 90% of airborne particles without impacting air flow
  • Electrostatically charged, pleated filters capture more harmful particles, last 3x longer than fiberglass models, and are 100% manufactured within the United States
  • Industrial grade beverage board (recyclable) frames with dual wire backings improve structural integrity and outperform standard cardboard designs
  • If you receive items with a different label, frame, or media than what is pictured, please note that any such alteration is purely cosmetic and your filter will still function exactly as described

The FilterBuy 20x25x4 MERV 8 Pleated AC Furnace Air Filter is a current filter with exceptional performance features. This furnace filter is designed for residential use.

Its frames are made from beverage boards. This means that it remains functional for a long time and can withstand the effects of moisture.

Also, it has a surface that is made of 100% synthetic materials. The surface is charged so that it can attract all contaminants that are found in the air. Also, the strands of this furnace filter are pleated. The pleating maximizes the surface area to ensure that 90% of the particles are trapped.

However, this furnace filter, like any other excellent product, does have weaknesses. The main drawback that is associated with this furnace filter is its low MERV rating of 8.

If you are keen on getting a furnace filter with a high MERV rating, you will be forced to look for alternatives.


  • The filter frames last for a long time because they are made from a beverage board
  • The surface of the furnace filter is charged to attract contaminants
  • The furnace filter lasts for up to three months


  • 8 MERV is relatively low


20x25x4 furnace filters can be the perfect device for combating allergens, odors, dust, and the presence of any other contaminants in your home.

Such furnace filters are longer lasting than those which are thinner. It is because they have larger surface areas. However, your 20x25x4 furnace filter’s performance is directly determined by its MERV rating and not the thickness.