How Often Do You Need to Change the Air Filter on Your Heating and Cooling Systems?

The 5-inch-thick Lennox Healthy Climate CarbonClean 16 lasts about 12 months, while the 1-inch Filtrete MPR 1900 needs replacing every three months or so. You can also find washable filters, which last longer (some are claimed to last several years), but they need to be cleaned every month—and none of the models we’ve tested earned a CR recommendation.

Before you replace a disposable air filter, check its condition. If it looks clean, it can be used a bit longer. But if it’s visibly dirty, it’s time to replace it.