best 18x20x1 air filters

Best 18x20x1 Air Filters Guide

The air in the area I live in is somewhat polluted, and my HVAC’s original air filter struggled to capture the pollutants causing my respiratory problems. That’s why I had to test some of the best 18x20x1 air filters to discover the model that could improve the air quality in my home and maximize my HVAC system’s cooling and heating efficiency.

Using the 18x20x1 air filters produced by different brands has also taught me that the best model on the market isn’t necessarily the right option for my unit. So, over the years, I learned how to pick a HVAC air filter that can keep the air in my home clean without putting too much stress on the HVAC system.

In this article, I’ll share the knowledge I acquired using different 18x20x1 air filters and help you choose a model that is the right fit for your air conditioner, heat pump, or furnace.

Bottom Line Up Front

Choosing a replacement filter for a cooling or heating unit for the first time can be challenging. So instead of experimenting with filters made by relatively unknown brands. I recommend getting a model produced by a renowned brand like the Filtrete Micro Allergen Defense Air Filter or Nordic Pure Air Filters, but only if you’re sure that they won’t restrict your unit’s airflow.

Also, Filterbuy Odor Eliminator Air Filters might be a good option if you’re looking for a model that can neutralize cigarette smoke or cooking smells.

My Top Picks At a Glance

Model MERV rating Filter media material Price range
Filterbuy Odor Eliminator Air Filters 8 Pleated synthetic $$$
Filtrete Micro Allergen Defense Air Filters 11 Electrostatically charged synthetic media $$$
Carter Washable Air Filter 8 Polypropylene $$
Nordic Pure Air Filters 12 Electrostatically charged synthetic media $
Aerostar Pleated Air Filters 11 Pleated electrostatic synthetic media $
AIRx Allergy Pleated Air Filters 11 Synthetic gradient media $$
Crisp Filters Air Filters 8 Pleated synthetic $
Flanders PrecisionAire Air Filters 8 Synthetic $
Filterbuy Air Filters 8 Pleated synthetic $$$

Types of 18x20x1 Air Filters

The quality of media material is the first and, in my opinion, the essential factor that ultimately determines the 18x20x1 air filter’s performance capabilities. So, checking the model’s filter media material can help you estimate how efficient it is at trapping microscopic and macroscopic air pollutants.

Types Air Filter

Besides the quality of the material, the media’s surface size also affects the filter’s efficiency. 18x20x1 air filters can be divided into the following categories based on the filter media material and design:

  • Fiberglass – The filtering capacities of models with fiberglass media are limited as most models struggle to capture particles smaller than 3 microns. Their price makes them an attractive option for homeowners who change air filters more than once a month.
  • Synthetic – Air filters with synthetic filter media are by far the most common. In addition, most models have pleated media designs that improve their air filtration capacities.
  • Electrostatically charged – These models usually have polypropylene or polyester media material that generates strong electrostatic fields. Some air filters with synthetic pleated media can also be electrostatically charged.

Air filter sizes

18x20x1 Air Filters

Assuming that all 18x20x1 air filters have the same dimensions was one of the biggest mistakes I made while searching for the first replacement filter for my HVAC system.

Soon enough, I realized that the model’s nominal size only serves as a guideline indicating its compatibility with grilles or registers with approximate 18x20x1 dimensions. The difference between the filter’s nominal and actual size varies from 0.5 to 0.75 inches.

Top tip: Don’t buy a six-pack of 18x20x1 air filters if you’re not sure they fit on your cooling or heating system’s vent. Purchase one or two filters instead and check if you can install them on your unit. 

Most brands include the filter’s actual size in the product description, so finding this information shouldn’t take much time. The easiest way to determine the actual size of a replacement air filter you need is to measure the dimensions of the old filter and the vent.

Continue reading related guides if you’re looking for a specific Air Filter Size:

Filtering efficiency ratings

The air that passes through a filter carries a certain amount of microscopic and macroscopic pollutants. The filter’s ability to retain those particles depends on the quality and design of the media material.

Following this train of thought, it’s easy to conclude that the best 18x20x1 air filter for your HVAC system is the one that can capture the highest percentage of air pollutants. However, models with high-efficiency ratings can restrict the unit’s airflow and increase its power consumption.

Filtering Efficiency Ratings

All 18x20x1 air filters produced by industry-leading brands have ratings that indicate their efficiency. Here are the most common air filter ratings:

  • MPR – This rating only applies to models manufactured by the 3M brand. It measures the filter’s ability to retain particles in the range from 0.3 to 10 microns on a scale from 100 to 2800.
  • MERV – MERV ratings of air filters designed for residential use vary from 5 to 16. Most HVAC systems use filters with MERV 8 ratings as they can trap dust or pollen efficiently without affecting the unit’s airflow. Models with higher MERV ratings can capture viruses or allergenic particles.

Continue reading to learn more about MERV ratings.

Check out more Air Filter guides based on MERV ratings:

Key features of 18x20x1 air filters

A variety of contextual factors, such as the climate, air humidity levels in my home, or my sensitivity to allergenic particles, play a vital role in my decision-making process. Each of these factors helps me determine which features a replacement air filter for my HVAC system should have.

So, for instance, if you live in a region with a humid climate, the filter you choose should have a rigid frame and moisture-resistant media to prevent warping or mold growth. Choosing a washable model over a disposable one might be a good option if you often use your cooling or heating system.

Top tip: Consult an HVAC technician before opting for an air filter with a MERV rating considerably higher than the one you’re replacing.

The quality of the wire grid that keeps the filter media in place is another factor you should consider because models that don’t have high-quality wire backing don’t last long.

Cost and upkeep requirements

I change the air filter on my HVAC system every month during the cooling and heating seasons. Still, I think the best way to determine how often you should change your furnace’s or heat pump’s air filter is to perform regular visual inspections.

Besides biweekly checks, disposable air filters don’t have any upkeep requirements, and most models have a 90-day lifespan. Washable air filters can last for several years, and they can replace over thirty disposable filters.

Filter Air 90 Day Lifespan

The reusable air filter’s cleaning frequency depends on the amount of dirt it can absorb, so if you have a model that can absorb less than ten grams of dirt, you’ll have to wash it every 30 to 45 days.

The cost of a single 18x20x1 air filter ranges from $5 to $20, while the average price for a six-pack of these filters is around $60.

Selection criteria

I understand that everyone has different expectations from a replacement air filter. That’s why my goal during the selection process was to identify the models best suited for homeowners with different air filtering requirements.

I had to utilize a variety of parameters to achieve this goal and shortlist the best 18x20x1 air filters suitable for different contexts. Let’s take a look at the key factors I relied on throughout the selection process:

  • MERV rating – This criterion has helped me identify the models with varying efficiency levels and exclude all air filters with MERV ratings above 12 or below 8.
  • Price range – The final selection includes both affordable and expensive air filters that can fit all budgets.

Top 9 18x20x1 air filters

Filterbuy Odor Eliminator Air Filters

Filterbuy Odor Eliminator Air Filters

The MERV 8 rating indicates that the Filterbuy Odor Eliminator Air Filters can’t trap viruses or microscopic allergenic particles. Still, the filter’s electrostatically charged synthetic pleated media captures more than 90% of pollen, dust, mold, or dander particles that pass through it.

Filter media enriched with activated carbon also neutralizes cooking smells and other house odors. This Filterbuy’s model is heat and moisture resistant, so moderate exposure to high temperatures or humidity doesn’t affect its performance.


  • The filter has dual-wire backing that prevents media sagging
  • Durable beverage board frame
  • It doesn’t cause pressure drops or restrict airflow
  • It’s compatible with most cooling and heating systems


  • The discrepancy between the filter’s nominal and actual size is 0.5-inches

Filtrete Micro Allergen Defense Air Filter

Filtrete Micro Allergen Defense Air Filter

Getting a four-pack of the Filtrete Micro Allergen Defense Air Filters will immediately affect the air quality in your home. Manufactured by one of the industry-leading brands, these filters remove close to 95% of macroscopic and microscopic particles from the air.

Their electrostatically charged media has a vast surface due to its pleated design that enhances their air-filtering capacities. Their rigid cardboard frame prevents warping and enables you to use them in hot or humid conditions.


  • Excellent air filtering capabilities
  • A simple three-step installation process
  • Eco-friendly design
  • It helps alleviate allergy symptoms


  • A short lifespan during cooling and heating seasons

Carter Washable Air Filter

Carter Washable Air Filter

Unlike disposable air filters, the Carter Washable Air Filter can hold up to 165 grams of dust, so you won’t have to clean it monthly. The electrostatically charged woven polypropylene media has a high arrestance rate as it can capture close to 95% of macroscopic air pollutants.

This Carter’s model has a low air resistance rating and doesn’t restrict the unit’s airflow or increase its power consumption. The metal mesh backing protects the media from heat or humidity, while the filter’s anodized aluminum frame prevents bending.


  • This filter can last for years
  • It doesn’t lose its air filtering capabilities over time
  • Washing this filter is easy
  • An affordable price


  • It struggles to filter microscopic particles

Nordic Pure Air Filters

Nordic Pure Air Filters

An excellent combination of affordability and performance capabilities make the Nordic Pure Air Filters an excellent option for homeowners who suffer from allergies or respiratory illnesses. This MERV 12 model can trap viruses, pet dander, or smog with the same level of efficiency.

Even though the pleated electrostatically charged synthetic media improves the air quality, it can restrict the unit’s airflow and lower its cooling capacities. These disposable air filters don’t last long because they accumulate dirt quickly.


  • The filter performs well in hot and humid conditions
  • It captures a high percentage of microscopic allergenic particles
  • A strong frame


  • Dense filter media lowers the unit’s cooling or heating efficiency

Aerostar Pleated Air Filters

Aerostar Pleated Air Filters

Despite having a MERV 11 rating, Aerostar Pleated Air Filters have low airflow resistance. Their pleated synthetic media has a large surface and a strong electrostatic field that attracts microscopic particles such as smog or sneeze aerosols.

However, this air filter can’t capture viruses and bacteria or neutralize odors. The lifespan of these air filters during the summer or winter months is thirty days, and you’ll have to change them often to keep the air quality in your home at the same level.


  • This filter can capture particles smaller than a micron
  • An excellent value for money
  • Installing and replacing this filter is easy
  • It enhances the unit’s cooling or heating performance


  • A short lifespan

AIRx Allergy Pleated Air Filters

AIRx Allergy Pleated Air Filters

AIRx Allergy Pleated Air Filters are compatible with cooling and heating appliances produced by industry-leading brands like Trane, Rheem, Lennox, or Goodman. This MERV 11 model has electrostatically charged synthetic pleated media that traps 1 to 10-micron particles.

The filter is heat-resistant, and its operating temperature range spans from 180F to 225F. Media material is also moisture-resistant, so its ability to retain air pollutants isn’t affected in humid conditions. Its frame made of a double-beverage board doesn’t bend even when exposed to high pressure.


  • It performs well in adverse conditions
  • Eco-friendly design
  • A good fit for households with pets
  • It’s compatible with a variety of cooling and heating systems


  • The filter can only capture particles larger than a micron

Crisp Filters Air Filters

Crisp Filters Air Filters

You should consider a budget-friendly option like the Crisp Filters Air Filters if you don’t have high air filtering expectations from your heating or cooling system.

Even though these filters can’t capture a high percentage of microscopic particles, they can still help you reduce the amount of dust and pollen in your home.

These MERV 8 filters have pleated synthetic moisture-resistant media, so you don’t have to worry about replacing them if they’re exposed to humidity.


  • Suitable for most households
  • Synthetic media material prevents mold growth
  • These filters don’t cause pressure drops


  • It can’t absorb cigarette smoke

Flanders PrecisionAire Air Filters

Flanders PrecisionAire Air Filters

Although they can’t deliver high-end performances and trap viruses or allergenic particles, Flanders PrecisionAire Air Filters still meet the air filtering needs of most homeowners. These filters have clay-coated frames that aren’t prone to warping in hot and humid environments.

Pleated media material captures all common air pollutants like dust, pet dander, or mold, and it can accumulate up to ten grams of dirt during its three-month lifespan. The wire backing extends the product’s lifespan by preventing its media from moving.


  • A 12-pack of these filters lasts for more than a year
  • A sturdy construction
  • Pleated media design
  • These filters are compatible with most heating and cooling systems


  • It can’t capture microscopic particles

Filterbuy Air Filters

Filterbuy Air Filters

I think buying a two-pack of Filterbuy Air Filters can help determine if you can fit them on your furnace’s or AC’s vent. It will also allow you to test their air filtering capabilities and see if they can improve air quality in your home.

This Filterbuy model has a MERV 8 rating and can only capture relatively large air pollutants like dust or mold. The filter’s beverage board frame and pleated synthetic media are heat and moisture resistant.


  • Filter media has a powerful electrostatic field
  • This filter is made of recycled materials
  • It improves the unit’s performance


  • More expensive than most MERV 8 air filters

Frequently asked questions about 18x20x1 air filters

Question: Does mold grow on 18x20x1 air filters?

Answer: Yes, mold can grow on these air filters if they’re not replaced frequently.

Question: How to check the MERV rating of the 18x20x1 air filter I am replacing?

Answer: Most brands include the model’s MERV rating on the filter. However, if the 18x20x1 air filter you’re replacing doesn’t have a MERV rating on it, you can find its model name and check its MERV rating on the manufacturer’s website.

Question: Can I use my heating or cooling system without a 18x20x1 air filter?

Answer: Yes, you can, but only for a short time. However, using the unit for more than six hours without an air filter will cause damage to a cooling or heating system.

I hope this guide has helped you find the best 18x20x1 air filter for your AC, heat pump, or furnace. Please go through our guide to the best ventilation systems to find out how they can improve air quality in your home.

My verdict: Which 18x20x1 replacement air filter should you get?

I think that a replacement air filter should have a similar efficiency rating as the filter you’re replacing. So, if you’re currently using a MERV 8 filter, upgrading to a MERV 14 model without consulting an HVAC technician could limit the unit’s cooling or heating capacities and inflate your monthly utility bill.

Despite their excellent air filtration capabilities, the Filtrete Micro Allergen Defense Air Filter or Nordic Pure Air Filters are only a good choice if you’re sure they won’t restrict the unit’s airflow.

Getting a MERV 8 model like Filterbuy Odor Eliminator Air Filters is a safer choice as it won’t affect the cooling or heating system’s performance.

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top