The air filter is the cheapest part of your heating and cooling system — and one of the most important. A clogged filter chokes airflow, makes the system work harder, pushes up your electric bill and is behind a surprising number of service calls. In Terrell, where the AC runs for much of the year and spring pollen coats everything, filters load up faster than the package suggests.
The short answer
- Standard 1-inch pleated filters: every one to three months
- 4- to 5-inch media filters (in a cabinet at the furnace or air handler): every six to twelve months
- Washable or electrostatic filters: rinse and dry them about once a month
Those are starting points. The right interval for your home depends on how hard the system runs and how much dust and dander is in the air.
When to change it more often
Lean toward the short end of the range — or check monthly — if any of these apply:
- You have dogs or cats, especially ones that shed
- Someone in the house has allergies or asthma
- You're remodeling, or there's construction nearby
- It's the middle of summer and the AC is running nearly nonstop
- Your home is on a dusty road or in a neighborhood that's still being built out
How to check your filter
Slide the filter out and hold it up to a light. If you can't see light through it, it's time for a new one. When you install the replacement, make sure the arrow on the frame points toward the unit (in the direction of airflow), and write the date on the edge with a marker so you know when you changed it last.
Where is my air filter?
In many Texas homes with an attic or closet unit, the filter sits behind a return-air grille in a hallway wall or ceiling. In others it slides into a slot at the furnace or air handler itself. Some homes have more than one return, and each one has its own filter — if you've only been changing one, check for others.
Choosing the right filter
Filters are rated by MERV (Minimum Efficiency Reporting Value). Higher numbers catch smaller particles, but they also restrict more airflow:
- MERV 1–4: basic fiberglass filters that mainly protect the equipment from large debris.
- MERV 8–11: the sweet spot for most homes — they capture pollen, dust and pet dander without straining the blower.
- MERV 13: catches finer particles like smoke, but can restrict airflow in systems that weren't designed for it. Ask a technician before upgrading.
Buy the exact size printed on your current filter's frame, and make sure it fits snugly — air that slips around the edges skips the filter entirely.
What happens if you skip it
A dirty filter does more than let dust into the house. Restricted airflow can cause the indoor coil to ice over in summer (one of the most common reasons an AC freezes up), make a furnace overheat and shut itself off in winter, and leave dirt on the coil and blower that a new filter won't fix. Over time, that extra strain shortens the life of the equipment and raises your energy bills.
If your system is already blowing warm air or icing up, read why an AC freezes up or schedule AC repair. We check the filter on every visit, and a seasonal HVAC tune-up is a good time to make sure you're using the right size and rating for your system.
