When to Change Your Air Filter (and How to Choose the Right One)

Changing the air filters in your HVAC system regularly is important not only for the air quality in your home, but also for saving money on your energy bill, as well as maintenance costs down the road on your system. A worn-out or clogged filter makes the fans in your circulation system work overtime to push air through it, so it can cause excess wear and tear on your system and cost more to run.

How to choose the right air filter

Choosing the right filter is easier than you might think. To find the size, just look at the frame of the filter that’s already in the unit. The size and type should be written on the side of the filter. There are a few different types of filters, so choosing the right one depends on how often you want to change it and sometimes on whether you have pets, if you have allergies, and if you live in an area where wildfire smoke is a concern.

Most residential homes don’t have HVAC systems that are compatible with HEPA filters because these require more power to get air through. So the two basic types are a flat-panel fibreglass filter and a pleated media filter. There are also washable filters, but these tend to have a low MERV (Minimum Efficiency Reporting Values) ratings and a higher incidence of developing mould and mildew.

A flat panel filter is cheaper, but will have a lower MERV rating — between 2 and 3 — and needs to be changed more often. In the long term, these filters don’t do as good of a job treating your air and will need to be replaced more often. A pleated filter will have a higher MERV rating — between 7 and 13 — and need to be replaced every 60 to 90 days. For most people, this filter type will be the best option.

What to know about an air filter’s MERV rating

If you have pets or suffer from allergies, you should change your filter more frequently. If you live in a place where wildfire smoke is a concern, it’s a good idea to change your filter more frequently when smoke is present and also to have an extra filter or two on hand before wildfire season starts. Once there is a lot of smoke, local stores can sell out quickly, so preparing ahead of time is important.

If you’re not sure whether it’s time to change your filter yet, take it out and look at it to see how clogged it is. For stronger filtering for smoke and pollen, a higher MERV rating is recommended (MERV 13 or better). For pollen, MERV 8 or better is recommended. If you’re planning on doing a home improvement project where you will be sanding and creating lots of dust, you can opt to use a cheaper flat panel filter during the project and then change it out for a better quality filter when you’re done. This will protect your system and your lungs from the excess dust, but won’t cost as much as replacing a higher quality filter.

How to change your air filter

To change your filter, turn off your HVAC system either from the thermostat, or from the breaker panel. Then, locate your filter either in your air handler, utility closet, attic, basement, or in a return duct where your system sucks air in through a vent. Open up the spot where your air filter goes, slide the old one out, and put the new one in place, making sure that the arrows on the frame of the filter are pointing in the direction that the air flows through the system. Then, close the system and turn it back on.