The typical 1” thick furnace filter usually indicates that it is good for “up to” 90 days. The key wording is “up to.” Depending on frequency of use and cleanliness of your ductwork, you may get 90 days out of your furnace filter. But, usually the filter needs to be replaced sooner than that. We recommend checking your furnace filter monthly and replacing when the filter has a noticeable layer of dirt across the surface.

This will improve the performance of your system and prevent costly breakdowns which can occur when the system is left to run with a clogged furnace filter. The filters will pay for themselves in the long run if replaced regularly.