Comparing Furnace Filters

How Do I Compare Furnace Filters?

There are a lot of furnace filters out there, which means it can sometimes be a bit overwhelming when you need to buy replacement filters. No worries though! You’ll be shopping savvy and breathing easy by the time you’ve finished reading this article.

Keep these key components in mind when you compare furnace filters:

  • Dimensions
  • Change Frequency
  • MERV Rating
  • OEM & Aftermarket Filters
  • Washable
  • Custom Air Filters

Dimensions: Air filters have dimensions printed on the filter frame and typically appear in the following formats: 16″ x 25″ x 1″ or 20″ x 25″ x 1″. This combination of numbers is the filter’s nominal size. If the numbers are missing, then measure the outer dimensions and round up each number to the nearest inch. This gives you the nominal measurement so you can replace the filter with one that fits the system properly.


Always make sure the replacement air filter is the correct size for your furnace. Heating, Ventilation, and Air Conditioning (HVAC) units need good airflow for the system to work at its best. When airflow resistance is low, your home’s air circulates more, helping your HVAC system to work more efficiently. Using a filter that’s too small for your cooling or heating system can restrict airflow or create high airflow resistance. Always choose an air filter sized correctly for your HVAC unit.

Like refrigerator water filters, air filters are essential tools for a healthy household. Both remove harmful impurities and help to improve daily living. Choosing the right air filter can make a significant difference in your home’s air quality.

Change Frequency: Different furnace filters may recommend varying change frequencies. For instance, most 1″ furnace filters should be changed every 1 – 3 months. On the other hand, 4″ and 5″ filters are capable of lasting up to 9 – 12 months.

The change frequency is not only important to identify before purchase, but also after so that you are aware of when you need to change your furnace filter next.

MERV Rating: The MERV rating offers the most evident difference between furnace filters. This essentially means furnace filters with higher MERV ratings filter out more particles from the air than furnace filters with lower MERV ratings.

When shopping for an air filter, consider the job you need to be performed. Is there someone in the home with allergies or asthma? The U.S. Environmental Protection Agency reports a medium efficiency filter with a MERV rating ranging from five to 13 is reasonably efficient for removing small to large airborne particles like pollen and dust.


Pet owners may want to consider a filter with a MERV rating of 11, typically good for reducing pet dander, which can aggravate allergies. Filters with a MERV 13 and higher are designed to remove particles such as mold spores and smoke, as well as pollen, dust and more. These are a good choice for people suffering from severe allergies, asthma or other respiratory issues.

OEM & Aftermarket Filters: When separate air cleaners are installed in HVAC systems, there are OEM (Original Equipment Manufacturer) and Aftermarket options available. What’s the difference between the two?

OEM means the furnace filter and the air cleaner were manufactured by the same company.

Aftermarket merely means the furnace filter was manufactured as a physical counterpart of the original furnace filter. Aftermarket furnace filters offer a variety of features that may not be available from the manufacturer, such as carbon odor block, easier-to-change design, and higher or lower MERV ratings

Washable: Some popular furnace filter sizes have a washable filter option. A reusable filter can be washed and used multiple times, offering potential money savings. While you may never have to replace your furnace filter, the main disadvantage to washable filters is you don’t get as high levels of filtration (high MERV ratings) from them.

Custom Air Filters: A custom air filter can be designed to fit your household’s exact needs and size specifications. Unlike common nominally sized filters, custom filters are made to the exact measurements you specify. You can purchase custom air filters on our website.

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3 thoughts on “How Do I Compare Furnace Filters?”

    • Furnace filters, air filters, air conditioning filters, and HVAC filters are all names for the same type of product. A furnace filter is placed into your indoor air filtration system to remove unwanted particles from contaminating your indoor air supply.

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