Air Conditioner Filter Replacement 101

Your central air conditioner filter plays a big role in helping your HVAC system operate at optimal performance. Replacing it regularly is an important part of home AC maintenance.

The filter for an air conditioner filters out dust, pollen, pet hair, and other household pollutants before they can get to your HVAC system. Your air handler or furnace draws in air from inside your home as it begins the cooling process. By filtering out airborne particles, a filter promotes a system’s optimal performance.

Clogged or dirty filters can lead to decreased performance, a frozen evaporator coil, and even a system shutdown. You can avoid many of these problems by making it a point to change the HVAC air filter regularly.

We’re focusing on ducted HVAC systems here. You can find the air conditioner filter located inside your home, next to the furnace or air handler. It’s sometimes called a furnace filter because of the location. You may also have a filter located on a wall or the ceiling behind a large air vent.

Most central air conditioner filters are disposable and are not meant to be cleaned. If you have a window air conditioner or portable air conditioner, consult the owner’s manual. If you have a mini-split air conditioner/mini-split system, visit our page on mini-split filters.

Follow these directions for how to change an air conditioner filter.

1. Turn off the HVAC system.
2. Remove the filter vent cover or open the door to the filter cabinet.
3. Remove the old filter and dispose of it.
4. Insert the new filter with the arrow pointing to the furnace or air handler (the arrow should point in the direction of the airflow). You can mark an arrow on your furnace or air handler with a Sharpie to help you remember which way to insert the filter.
5. Put the vent cover back on/close the cabinet door.
6. Turn the HVAC system back on.

This is a great question to be asking, because there is a wide range of air conditioner filter sizes, and you want yours to fit just right. The easiest way to know what filter size you need is to remove the existing filter (after turning the HVAC system off). It should have measurements listed on one or more edges.

To be sure you always have the right filter on hand, consider signing up for automatic delivery with Trane Filters powered by FilterTime™. Using the wrong size filter can damage your system and lead to sub-optimal indoor air quality (IAQ).

Plan on changing the filter every 30-90 days, depending on the quality of the filter, whether it’s pollen season, and if you have pets. If you have a programmable or smart thermostat, it may display an alert when it is time to change the filter. You can also use the Trane Home App to remind you.

In addition to changing your air filter, you should schedule regular HVAC maintenance with your local Trane dealer. Ask about a maintenance plan to provide timely tune-ups to your heating and cooling system.

Anne Fonda, Content Writer at Trane Technologies

A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

Expert review by Mark Woodruff, Senior Product Manager, Ducted Outdoor

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