How to Change Your HVAC Filter
A dirty HVAC filter reduces airflow, increases energy bills, and worsens air quality. Learn how to find, size, and replace your filter in under 10 minutes — the easiest home maintenance task there is.
Repair & Refinish Team
Published March 3, 2026 · Updated March 20, 2026
What You'll Need
- Step stool or ladder (if filter is in ceiling)
- Flashlight
- Replacement HVAC filter (correct size and MERV rating)
- Permanent marker (to write install date on filter)
Cost Estimate
Budget
$5
Mid-Range
$15
Premium
$30
An HVAC service call costs $75-$150 and usually includes a filter change, but you can do it yourself in 5 minutes for $5-$30 per filter.
Step-by-Step Instructions
Locate Your HVAC Filter
Step 1 of 5Filters can be in several locations depending on your system. The most common spots are: inside a return air grille on a wall or ceiling, in a slot at the furnace or air handler (between the return duct and the blower), or in a ceiling-mounted return vent. If you have multiple return vents, each may have its own filter. Check every return vent in your home.
Not sure which vents are returns? Turn the system fan on and hold a tissue near each vent. If the tissue is sucked toward the vent (rather than blown away), it's a return vent with a filter.
Remove the Old Filter and Note the Size
Step 2 of 5For wall or ceiling grilles, open the grille (most have latches or swing open). For furnace filters, slide the access panel open. Pull the old filter out and look at the size printed on the frame — it will show three numbers like 16x25x1 or 20x20x4 (width x height x depth in inches). Write this size down or take a photo. This is the filter size you need to buy.
Check the Airflow Direction Arrow
Step 3 of 5Every HVAC filter has an arrow on the frame showing the correct airflow direction. The arrow should point TOWARD the furnace or air handler (in the direction the air flows). For wall and ceiling return grilles, the arrow points into the wall or ceiling (away from the room). For furnace-mounted filters, the arrow points toward the blower motor. Getting this backwards reduces filter efficiency.
Installing the filter backwards (arrow facing the wrong way) significantly reduces its effectiveness. The filter media is layered directionally — the coarser side should face the incoming air.
Insert the New Filter
Step 4 of 5Slide the new filter into the slot with the airflow arrow pointing in the correct direction. The filter should fit snugly without gaps around the edges — air bypassing the filter defeats its purpose. If the filter is slightly loose, check that you have the right size. Close the grille or furnace access panel. Write the installation date on the filter frame with a marker so you know when to replace it next.
Buy filters in bulk (packs of 4-6). It's cheaper, you always have one on hand, and it reminds you to change them regularly. Set a calendar reminder for every 90 days.
Dispose of the Old Filter and Set a Reminder
Step 5 of 5Place the old filter in a garbage bag to contain the trapped dust and allergens, and dispose of it in your regular trash. If you have washable/reusable filters, rinse them with water, let them dry completely (at least 24 hours), and reinstall. Set a recurring reminder on your phone to check the filter every 30 days — hold it up to a light, and if you can't see light through it, replace it.
Recommended Products
MERV 12 rating catches dust, pollen, mold, pet dander, and smoke. Electrostatic charge attracts particles. 90-day replacement cycle. Available in all standard sizes.
Made in USA. Excellent balance of filtration and airflow. Electrostatically charged synthetic media. Available in over 100 sizes. Best value MERV 11 filter.
High-capacity 4-inch filter that lasts 6-12 months between changes. MERV 11 rated. Fits Honeywell media air cleaners and many standard 4-inch filter slots.
Affiliate Disclosure: We earn a small commission when you buy through our links at no extra cost to you.
Tips & Warnings
- Buy a year's supply of filters at once. A 4-pack or 6-pack is significantly cheaper per filter and ensures you always have one ready.
- MERV 11 is the sweet spot for most homes — it catches dust, pollen, mold, and pet dander without restricting airflow excessively.
- If you have pets, check the filter monthly. Pet hair and dander clog filters 2-3 times faster than in pet-free homes.
- Write the install date on the filter frame with a marker. It's easy to forget when you last changed it.
- Never run your HVAC system without a filter. Dust and debris will accumulate on the evaporator coil and blower motor, causing expensive damage.
- Don't use a filter with a higher MERV rating than your system supports. High-MERV filters restrict airflow, which can cause the evaporator coil to freeze or the blower motor to overheat.
- If your filter is clogged solid after only 2 weeks, check your ductwork for leaks that are pulling in extra dust from attics or crawl spaces.
Frequently Asked Questions
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