How to Install an Air Conditioner Filter: 7 Simple Steps

Establishing their location could be the most time-consuming part of learning how to install air conditioner filters. The filter location depends on your system and home setup. Some are located in the air vents behind a grille on the ceiling, wall, or floor, and others can be near or inside the blower compartment of the actual AC unit. You might have to do some detective work if you don't have the system manual.

Before inspecting the filter, turn off the air conditioner unit. This prevents accidents while you fiddle with parts, debris from entering your HVAC system, and dirty air from escaping while the filter is out.

If there isn't a shutoff switch on or beside the air conditioner unit, turn off the power to the HVAC system in the circuit breaker box.

Inspect the old air conditioner filter so you can buy the correct size replacement. HVAC filter sizes are wide-ranging, and the system needs a secure fit to operate effectively.

The size is sometimes noted on the side of the air filter. Other times, you'll need to measure the filter's length, width, and thickness with a tape measure.

Be aware that the nominal size on the filter box is a rounded-up version of the actual air conditioner filter size. Expect the advertised size to be 1/4- to 1/2-inch bigger than the measurements you get manually. 

You should be able to simply slide the old filter out of its compartment for replacement. If the filter is inside a vent in your wall or ceiling, out of arm’s reach, you will need a ladder for easy access, and you might need a screwdriver to remove the grille. If the filter has airflow arrows around the edges, note their position—this will help you fit the new filter correctly. 

Have a trash bag on hand to avoid loose dust dispersing around your room. 

Clean the air vent grille before installing the new air conditioner filter. This prevents the filter from getting dust-covered before you turn the unit back on.

Use your vacuum hose fitting to suck up large swathes of dirt and debris, then wipe away any remaining dust with a damp microfiber cloth. 

If you have the right size and position it in the right direction, the new filter should slide snugly into place. Those airflow arrows will act as a helpful guide—they should point outwards, away from the air ducts. 

Switch the HVAC system back on. If you've installed the air conditioner filter correctly, there shouldn't be any vibrating or humming noises resulting from a poor fit.