How to Know Which Filter Is Right for Your Furnace

Reviewed by Robert Tschudi
Updated June 1, 2022
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  • When picking the best furnace filters, consider price, MERV rating, and convenience

  • Most filters cost between $1 and $20 each

  • Regularly changing filters will decrease energy use and prolong your furnace’s lifespan

  • Choose between fiberglass, polyester, pleated, and washable filters

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Who knew such a tiny little furnace filter could have such a big impact? Your home’s air quality will differ, depending on the type of filter you choose, which means that opting for the right furnace filter is just as important as changing it every few months (more on this below). Read on to learn about a few factors to consider when picking the best furnace filters.

The Benefits of Changing Your Filters Regularly

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When it comes to a system as complex as your HVAC, a simple little furnace filter might not seem like that big a deal. But the reality is that your furnace filters are key to your heating and cooling system’s ability to function properly.

Dirty and clogged filters force your system to work incredibly hard just to maintain your desired temperature. Not only will this increase your energy use (and the utility bills to go with it), but it will also cause your system to break down faster.

“Many new home buyers get a home warranty, which is a good thing,” says Bob Tschudi, a Raleigh, NC-based general contractor and Angi Expert Review Board member. “However, if your HVAC system has a problem, the first thing the tech will look at is your filters. If they haven’t been regularly changed, the warranty is voided. It’s in your best interest to change out furnace filters every 90 days.”

Furnace fixes are costly, usually around $300 depending on the type of repair. You may even need to replace the entire system, which can cost you as much as $6,000 for an electric furnace and $12,000 for a gas furnace.

Factors To Consider When Picking a Furnace Filter

When it comes to choosing a furnace filter, there’s no one-size-fits-all strategy. Rather, it depends on the type of furnace and your family’s needs.

MERV Ratings 

If air quality is your top priority, then you’ll want to look for a filter with a high MERV value. The minimum efficiency reporting value (MERV) uses a scale from one to 20 to indicate the types and quantities of pollutants that the filter pulls from the air. As a rule of thumb, the higher the MERV rating, the better the filtration.

  • Up to MERV 6 catches lint, pollen, dust, dust mites, mold

  • MERV 8 filters everything from MERV 6 and under, plus pet dander, smoke, smog, allergens

  • MERV 12 catches all of the above plus bacteria and viruses

  • MERV 13 and up filters out all that and more (it’s good for people with severe allergies)

However, it’s important to note that not all HVAC systems can handle filters with higher MERV ratings. HEPA filters, for instance, are thought to remove 99.97% of particles from the air, but most residential systems cannot operate with these filters because the filtration screens are too dense to allow proper airflow through the system. Save HEPA filters for air purifiers designed explicitly for them.


If cost is your most important filter feature, opt for fiberglass filters. For around $1 each, you won’t have to break the bank to change these filters. They’ll grab large particles, but with a low MERV rating of between 1 and 4, they won’t do much to actually clean the air.

Polyester and pleated filters are still affordable but offer a higher level of filtration thanks to their 8 to 13 MERV rating. Averaging around $10 each, they’ll remove around 45% of contaminants.

Convenience and Sustainability

A washable filter offers both convenience and sustainability, as you won’t have to throw away your filters or replace them as frequently. You can reuse washable filters for up to a year or more. However, they can be costly (averaging around $20 per filter), and they aren’t the best for improving air quality since most have a MERV rating of 4 or less.

Without proper caution when cleaning and drying washable filters, they can easily collect mold, mildew, and funguses—all things we’d rather not have circulating in our homes!

How Often Should You Change Your Filter?

Changing your furnace filter is one of the cheapest, easiest, and most effective ways to maintain your HVAC. In general, you should plan to change your filter every 90 days at a minimum. However, you may want to do this more often in certain circumstances.

“All HVAC return registers are not the same,” says Bob Tschudi. “While the filters in some returns clog quickly, others do not. This means you’ll need to change some filters more frequently than others.”

If you have pets, smoke, or particularly high levels of pollutants in your home, you should consider changing your filters more often. It’s also a good idea to replace your filters frequently if anyone in your home has asthma or allergies. 

Though it’s not exactly common, mold can accumulate on your filters. Check your furnace filters for signs of mold if the air has a musty odor or if your family has water eyes, sneezing, a runny nose, or other signs of allergy irritation.

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