The air filter is the cheapest part of your heating and cooling system, and one of the easiest to forget. A dirty filter blocks airflow, which makes the system run longer and work harder.
The short answer
ENERGY STAR recommends you check your filter every month and change it at least every three months. Replace it sooner if it looks dirty.
In Arizona, many homes need a new filter more often than that:
- Air conditioning runs for much of the year, so more air passes through the filter.
- Dust storms and dry desert soil put more dust in the air.
- Pets, construction nearby or someone in the home with allergies all load a filter faster.
A good habit: check it on the first of every month. If it looks gray and you cannot see light through it, change it.
Where to find your filter
Filters are usually in one of two places:
- Behind a return grille on a wall or ceiling inside the house. This is the large vent that pulls air in, not one that blows air out.
- At the indoor unit in the attic, garage or a closet, in a slot near where the ductwork connects.
Some homes have more than one return, so more than one filter.
How to replace it
- Turn the system off at the thermostat.
- Read the size on the old filter’s frame, for example 16x25x1. Buy the same size.
- Note the arrow printed on the frame. It shows the direction air flows. Point it toward the indoor unit, away from the room.
- Slide the new filter in and close the grille or cover.
- Write the date on the frame so you know when you changed it.
Which filter to buy
Filters are rated by MERV. A higher number catches smaller particles, but a very dense filter can restrict airflow on some systems. If you are not sure what your system can handle, ask during your next maintenance visit.
Why it matters
A clean filter helps your system move air the way it was designed to. A clogged one can lead to weak airflow, longer run times and, in some cases, a frozen indoor coil in summer. If you change the filter and airflow still seems weak, call us to have the system checked.