Maintenance
How Often Should You Really Replace Your Furnace Filter?
May 30, 2026 · 5 min read
The printed interval on a filter box assumes an average home with no pets, no construction nearby, and moderate runtime. Very few homes are average. A one-inch pleated filter in a house with two dogs and a dusty street can be fully loaded in 30 days.
As a working baseline: one-inch filters every 30 to 60 days, four-inch media filters every six to nine months, and five-inch cabinet filters annually. Add pets, allergies, or nearby construction and cut those intervals roughly in half.
MERV rating matters as much as timing. Higher MERV catches finer particles, but a filter that is too restrictive for your blower starves airflow and raises energy use. Most residential systems are happiest between MERV 8 and MERV 13 — go higher only if the equipment and duct sizing were designed for it.
One habit worth building: write the install date on the filter frame in marker. It turns a guessing game into a five-second check.
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