Why it matters
Your heating and cooling system pulls all the air in the house through the filter. When the filter clogs, the system works harder, cools and heats less evenly, and wears faster. A clogged filter is one of the most common reasons an AC coil freezes.
Pick your schedule
- No pets, no allergies, mild weather: every 3 months.
- One pet or moderate use: every 2 months.
- Several pets, allergies or asthma in the home: every month.
- Peak summer or winter use: check monthly, because filters load faster when the system runs all day.
- Thick media filters (4 to 5 inches): every 6 to 12 months, or as the maker says.
Finding the right size
The size is printed on the edge of your current filter, like 16x25x1. Write it down or take a photo. The arrow on the filter points toward the furnace or air handler, in the direction air flows.
Which rating to buy
Filters are rated by MERV. A MERV 8 to 11 filter catches dust, pollen and pet dander and works with most home systems. Very high ratings can restrict airflow on systems not designed for them, so check with your HVAC technician before going above MERV 13.