Call Your Service Tech
From A.B. May
Call Your Service Tech
From A.B. May

back to blog

How to Change the Furnace Filter in Your Home

post img

One of the quickest and easiest ways to improve energy efficiency in your home is to regularly change your furnace filter. Follow these easy steps to have an efficient and healthy home.

How often should I change my Furnace Filter and Why?

Furnace filters collect dust and grime circulating through the air in your home. To make sure you are breathing in clean air, check your filter every three to four weeks.

  • If your furnace requires a non-pleated filter, replace it once a month.
  • If your furnace requires a pleated filter, replace it every two to three months.
  • If your furnace requires a 4-5″ media filter, replace it every four to six months–sometimes up to a year.

Read your furnace’s operating manual or our page on understanding air filters to learn more about furnace filter replacement intervals.

Why Do You Need to Replace A Furnace Filter?

If you notice your filter is dirty or damp, change it right away. Check for mold by holding it up to a light. If you see any spores growing, dispose of the filter immediately and replace it with a new one.

Where can I buy a filter?

It might feel like a like to stay on top of changing your filter. Fortunately, there are options to make it easier:

1. Use Amazon to purchase filters in bulk so you always have a fresh one handy with significant cost savings. Or use their Subscribe & Save feature to set up automatic deliveries when you want to change your filter. We recommend the higher-performance pleated ones for better performance and efficiency. For convenience, take a picture of your filter or take it with you to the store. We recommend a MERV rating of 6 or higher. MERV stands for Minimum Efficiency Reporting Value, which determines how well it’s able to filter out small particles.

2. Sign up for a Filterjoy subscription, a service that sends new filters right to your door at regular intervals. A.B. May customers can get a discount when you first sign up at It typically takes 2-5 business days for the first filter to arrive.

3. Set up reminders on your calendar or smart speaker and purchase filters from any hardware or big-box retailer when you need them. 

To find out of the size of your filter without measuring it, look for a label on the side of the unit. Typical sizes are 16x20x1, 16x25x1, and 20x25x1.



Locate the air filter slot on the HVAC unit

To locate the air filter, start at the air handler. From there, follow the ductwork back toward the furnace. The air filter slot will likely be along this path.

Turn Unit Off

To avoid harm to you and your system, turn the unit off using the switch. A red on/off button is typically located in the center of your unit.

Remove old filter

The old filter should slide easily out of the slot. Carefully remove the filter to avoid dust scattering on the floor. Seal the filter in a garbage bag and dispose of it.

Insert new air filter

The new filter should slide in easily. Is the new filter having a hard time sliding in? It may be the wrong size. Scroll back up to find out how to identify the proper size filter for you.

Turn the unit back on

Once the new filter is secure in the slot, turn the unit back on. Make sure everything is running properly. Using your thermostat, turn on the fan for a few hours to initiate airflow through the new, clean filter.

What Happens If You Put A Furnace Filter in Backwards?

If the furnace filter is not inserted properly, it will be unable to collect dust and grime. It will likely create issues for your system as well. If you think the filter is installed backward, remove it and turn it around before inserting it again.

For help with changing your Furnace filter, contact your Kansas City HVAC technician from A.B. May to schedule maintenance.

Our Promotions

PLUMBING $780 3/4 HORSEPOWER GARBAGE DISPOSAL Includes installation and 7-year parts warranty

Affordable Financing

  • Request Service

    Fill out the form below, and we’ll contact you shortly to schedule your home service appointment.

    Request Service

    • Please call for 24/7 emergency service.