The Complete Guide to HVAC Filter Replacement

Your HVAC filter does two jobs: protecting your equipment from dust and debris, and keeping the air you breathe clean. A clogged filter forces your system to work harder, raising energy bills and shortening the life of your furnace or air handler.

Most 1-inch pleated filters should be replaced every 60-90 days. Thicker 4-inch and 5-inch filters can often go 6-12 months. Homes with pets, allergies, or nearby construction should lean toward the shorter end of that range.

MERV (Minimum Efficiency Reporting Value) ratings run from 1 to 20. Residential systems typically use MERV 8-13. Higher isn't always better — very high MERV filters can restrict airflow in systems not designed for them, so check your equipment's manual before upgrading.

To find your filter size, check the cardboard frame of your current filter for three numbers (e.g., 16x25x1) — that's width x height x depth in inches. If it's illegible, measure the slot itself, since actual dimensions are often slightly smaller than the labeled size.