Air Filter Buying Guide
Getting Started

Heating and cooling consumes a big part of your utility bill. But it’s a small thing, the air filter, that keeps the entire 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 a breakdown.  If you're getting low airflow, check the air filter—a clogged filter can cut airflow to a trickle.

How We Tested

Consumer Reports tests air filters for homes with forced-air heating and cooling systems. We test air-flow 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 one-inch thick but some systems can accommodate filters two- to five-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 your and for your HVAC system.

Air Filter Pros and Cons

Pros:
Maintaining a system with 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 include a range of standard sizes, with a few that can adapt to fit different-sized filter-box or return-air openings.

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

Prices:
From $20 to $80 per filter. Annual replacement costs are typically $100 or less.

Terms to Know

MERV. Many whole-house filters list a minimum efficiency reporting value (MERV), developed by 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 Micro-Particle Performance Rating developed by 3M. It rates the filters on the ability to capture airborne particles smaller than 1 micron. The best filters have MPRs between 1500 and 1900.

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 an electrostatic filter, which uses an electrical charge to help trap particles, or a high-efficiency particulate-arresting (HEPA) filter can reduce the amount of dust blown through the heating system. That might help people with asthma or 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 backwards, which can block the flow of air instead of cleaning it. Here’s how to do the job properly in three simple steps.

What kind of filter do you have? Start by turning off the furnace. Remove the existing furnace filter, which will be located 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.

Time out! 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 was effective at removing dust, pollen, and smoke when air passed 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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