Heating & Cooling · 2026-06-17

How to Change Your HVAC Air Filter (and How Often to Actually Do It)

A simple, no-cost maintenance habit that protects your system, lowers bills, and improves the air you breathe.

Replacing your furnace or AC filter is the single easiest thing you can do to keep your heating and cooling system running well, and most homeowners can do it in under five minutes. Find the filter slot, usually in a return-air grille on a wall or ceiling, or in a slot next to the furnace itself. Note the size printed on the cardboard edge (for example, 16x25x1), then slide the old filter out and the new one in so the printed arrow points toward the furnace, in the direction the air flows. That arrow matters: a backwards filter sheds fibers and works poorly.

For a standard 1-inch filter, check it monthly and replace it roughly every 1 to 3 months. Replace it sooner if you have pets, allergies, or a lot of dust, and during heavy heating or cooling seasons. Thicker 4- and 5-inch media filters can last longer, often up to 6 months. A clogged filter chokes airflow, which makes your system work harder, raises your energy bill, and can cause the system to freeze up or overheat. You don't need the most expensive filter; a clean mid-range pleated filter beats a dirty premium one every time.

If airflow still feels weak after a fresh filter, or you notice musty smells or visible buildup coming from the vents themselves, the issue may be deeper in the system. That's a good moment to bring in a professional who can inspect the blower and ductwork rather than guessing.

Relevant resource: have someone inspect the ductwork.