HOW TO CHANGE AN HVAC FILTER: LOCATE IT, SIZE IT, REPLACE IT SAFELY
WHY CHANGING YOUR HVAC OR AC FILTER MATTERS
A clean filter protects indoor air quality, keeps airflow strong, and helps your system run efficiently. A dirty filter can raise energy costs, stress the blower motor, and allow dust to collect inside the equipment. Regular changes can reduce breakdowns and extend system life. If your home has allergy or asthma concerns, consistent filter changes help reduce fine particles.
Pro tip: Never run your system without a filter. If you remove a clogged filter and do not have a replacement, turn the system off until a new one is installed.
HOW OFTEN TO CHANGE AN HVAC FILTER
For most homes with 1-inch pleated filters, a 30–90-day cadence works well. Check monthly during heavy summer or winter use, and plan more frequent changes if you have pets, construction dust, or poor outdoor air quality days. Thicker media filters, like 4–5 inch cabinets, typically last longer. Always follow your system and filter guidance. Set a calendar reminder or write the install date on the filter edge so timing is easy to track.
WHERE TO FIND YOUR FILTER(S)
Some homes have more than one filter. Check these common spots:
- Return grilles in hallway ceilings or walls
- The air handler or furnace cabinet near the blower
- A media cabinet filter at the unit
- Each return grille in larger homes. If you are unsure, a technician can point out every filter during a quick visit.
HOW TO CHOOSE THE RIGHT FILTER
1) Confirm the size
Look for the size printed on the filter frame, for example, 16 × 25 × 1. If the label is missing, measure the filter's length, width, and thickness. (If the filter is missing, measure the slot's length, width, and thickness, then buy the nearest nominal size.)
2) Pick a MERV rating that fits your system
MERV describes particle capture performance. Many homes do well with MERV 8–13. Higher MERV usually improves capture but can add resistance to airflow, so verify your system can handle an upgrade before stepping up. If you are unsure, check your manual or ask a technician.
3) Choose thickness and style
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1-inch pleated filters are common and typically last 1–3 months.
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4–5-inch media filters often provide better overall filtration with less frequent changes, and they sit in a cabinet at the unit.
If airflow drops after a MERV upgrade, step down a rating or consult a pro. For whole-home solutions, explore Indoor Air Quality products, and consider the Pro Service Plan to keep maintenance on track.
TOOLS AND PREP CHECKLIST
- New replacement filter(s)
- Flashlight and tape measure
- Step stool or ladder for ceiling returns
- Screwdriver if the grille has fasteners
- Marker to write the install date
- Trash bag for the used filter
Safety first: Turn the system Off at the thermostat before removing the old filter. For cabinet work, you can also switch off power at the service switch or breaker.
STEP-BY-STEP: HOW TO INSTALL AN AC OR HVAC FILTER
Step 1: Locate the filter spot
Find each return grille and the filter slot at the air handler or furnace. Some homes have more than one, so check every return and the unit.
Step 2: Confirm size and airflow direction
Match the size from your old filter or your measurements. (You may have to wait till you have removed the filter to see the measurements.) Note where the blower is so you can install the filter with the arrow pointing toward the blower and into the duct or unit, not into the room.
Step 3: Turn the system off
Set the thermostat to Off while you handle the filter. If you open the equipment cabinet, also use the service switch or breaker.
Step 4: Remove the old filter
Open the grille or access panel, slide out the filter carefully, and place it directly into a trash bag to keep dust from re-entering the space.
Step 5: Insert the new filter
Slide the new filter into the slot with the arrow toward the equipment or duct. Ensure a snug fit with no gaps or buckling. Write the install date on the filter edge, then close and secure the grille or panel.
Step 6: Turn the system back on and check airflow
Return the thermostat to Cool or Heat and confirm air is moving normally at a few supply registers. If you hear whistling at the return or airflow seems weak after a higher MERV upgrade, reconsider the rating or ask a technician. If you have return-grille filters and a media filter, replace them all on schedule and avoid stacking filters in the same slot.
AFTER YOU REPLACE THE FILTER: QUICK CHECKS
- The grille or panel is closed securely, no rattles.
- The filter sits flat and the arrows face the correct direction.
- You recorded the change date and set a reminder.
- You have a spare on hand for next time.
WHEN TO CALL A PRO
- You cannot find the filter location, or the grille will not open.
- The filter collapses, whistles, or will not sit flat.
- Airflow drops after a filter upgrade.
- You see water, corrosion, or signs of mold at the unit or duct.
- Dust builds up fast even with regular filter changes.
KEEP COMFORT SIMPLE WITH PROACTIVE CARE
For easier maintenance, consider a seasonal plan with reminders and priority scheduling. For whole-home air solutions, explore Indoor Air Quality upgrades that complement your filter strategy.
