Air Filter Buying Guide

Heating and cooling probably constitutes a big part of your utility bill. But it’s one small thing—the air filter—that keeps the entire central air system humming along. A dirty filter can restrict airflow, preventing the system from working like it’s supposed to, and that can eventually lead to an equipment breakdown. If you’re getting low airflow, check the air filter—a clogged filter is one of the most common reasons.

The best air filters trap indoor pollutants such as dust, pet dander, and pollen, helping to clean the air in your home. That’s important because the concentration of air pollutants inside your home can be two to five times higher than concentrations typically found outdoors. And by typically, we mean on days when no heavy smog or wildfire smoke has seeped into your home. A good air filter can help with that, too. Any air filter that scores well in our tests is a good choice for clearing the air during smoke conditions.

Of course, air filters aren’t the only filters you should be monitoring and/or replacing to keep the air and water in your home clean. Here’s a rundown of the 12 filters you should be changing. For more information on the individual products that use filters, such as air purifiers, room air conditioners, and dehumidifiers, check out their dedicated buying guides.

Read on to learn more about our air filter tests and which type of filter is best for your forced-air heating and cooling system.

How We Test Air Filters

Consumer Reports tests air filters for homes with forced-air heating and cooling systems. We test airflow resistance, which measures how freely air flows through the filter. Our recommended models are the best at filtering dust, pollen, and smoke from the air without impeding the flow of air.

Most air filters are 1 inch thick, but some systems can accommodate filters 2 to 5 inches thick. In our tests, we found that the thicker the filter, the better it works and the longer the replacement intervals. That means it’s better for you and for your heating, ventilating, and air conditioning (HVAC) system.

Air Filter Pros and Cons

Changing out an air filter is easy. You slip out the old filter and slide in the replacement. Some are conventional fiberglass filters; others are pleated or electrically charged to pick up particles. (Note that the electrically charged versions are not actually electrically powered, even when they have names like Electroclean, and they don’t produce ozone.)

Air filters generally come in a range of standard sizes, with a few that can adapt to fit different-sized filter-box or return-air openings.

For thicker filters to fit, you may need to have your ductwork modified by a professional. The filters must be replaced every one to three months.

From $20 to $80 per filter. Annual replacement costs can be as low as $20 or as high as $200.

Terms to Know

MERV: Many whole-house filters list a minimum efficiency reporting value (MERV), developed by ASHRAE (formerly the American Society of Heating, Refrigerating and Air-Conditioning Engineers). The higher the number, the finer the filtration. The top performers in our tests typically have a MERV higher than 10.

MPR: This is the Microparticle Performance Rating, developed by 3M. It rates filters on their ability to capture airborne particles smaller than 1 micrometer. The best filters have an MPR between 1,500 and 1,900.

FPR: Home Depot uses its own rating system, on a scale of 1 to 10, called the Filter Performance Rating. The higher the number, the better it filters.

HEPA: Fitting a furnace with a HEPA filter can reduce the amount of dust blown through the heating system. (An electrostatic filter, which uses an electrical charge to help trap particles, can do the same.) That might help people with asthma and other chronic lung diseases, but there’s little evidence that other people need such filtration.

How to Change a Furnace Filter

Replacing a furnace filter is pretty simple once you know what you’re doing. There are ways to botch the job, however—for example, by buying the wrong size filter or putting it in backward, which can block the flow of air instead of cleaning it. Here’s how to do the job properly.

What kind of filter do you have? Start by turning off the furnace. Remove the existing furnace filter, which will be inside the furnace or inside the return air vent. Look for an arrow on the filter indicating airflow direction. Using a permanent marker, draw the airflow direction on the outside of the furnace, so you’ll always know the right way to install the filter. Then note the furnace filter size, which will be printed on the cardboard frame.

Check to see whether the filter is reusable. A filter that has a plastic frame is a reusable model. That means you have to clean it periodically with a vacuum and water, ideally outdoors. Let it dry completely before reinserting.

Get the right replacement. Furnace filters are sold at home centers, hardware stores, and online. Disposable ones are typically 1 or 2 inches thick. Check our ratings of furnace filters for a right-sized model that’s effective at removing dust, pollen, and smoke when air passes through it at both high and low speeds. We also test thicker furnace filters, some up to 5 inches, and they often provide superior air cleaning and long life. But if your furnace isn’t already equipped to handle a thicker filter, it will need to be modified by an HVAC professional.

Install the new filter. Look for the markings that tell you which side of the filter should face the furnace. Then slide the filter back into place and replace any cover that goes over it. Keep a record of the date so that you’ll know when it’s time to change the furnace filter again.

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