Best Air Filters for Your Furnace and Central AC - ConsumerReports.org

Hidden away in your basement or attic, the air filter in your HVAC system is something you probably don't think about much. But a good air filter keeps your furnace and central air conditioner humming along by protecting the mechanicals from dust and debris. And the best 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, according to the Environmental Protection Agency.

Below are the top air filters from CR's tests (grouped by their thickness and listed in alphabetical order). We gauge how well an air filter removes dust, pollen, and smoke from the air, and see how freely air flows through the filter at any fan speed. We also calculate the annual costs of replacement filters, based on the manufacturer's recommendation for when to change them (keep in mind: prices may vary by retailer; also, it may be cheaper if you buy filters in bulk).

"Thicker filters perform better in our tests and we found that you don't have to replace them as often," says Dave Trezza, who oversees CR's air filter tests. But not every HVAC system can accommodate a thicker filter—the most common size is 1 inch thick—though you can retrofit the ductwork of some systems to accept thicker filters.

Something else to keep in mind as you shop is the filtering grade given by the manufacturer. The most commonly used system applies a MERV number (minimum efficiency reporting value) to each filter, which was developed by ASHRAE (formerly the American Society of Heating, Refrigerating and Air-Conditioning Engineers). But 3M and Home Depot have each developed their own classification systems called MPR (microparticle performance rating) and FPR (filter performance rating) respectively. "No matter the grading system, the higher the number, the better the filter is at getting rid of air pollutants," says Trezza.

For more information on air filters, including some models to avoid, see our full air filter ratings and air filter buying guide.