Maximizing HVAC Efficiency And How Often to Change Your Filter

Air filters are one of the most vital parts of ensuring our home’s cleanliness, whether that’s through the air quality or maintaining tidiness. Many homeowners come to learn this and often do their best to keep their HVAC system’s air filter as clean as possible. Sooner than expected, the air filter becomes too dirty to simply clean quickly and needs replacing. 

But, how can you tell how often to change an HVAC filter, especially when every home is unique?

To help answer this question and a few others, we’ve compiled a guide of all the information. It’s important to remember that, like each home and homeowner, each HVAC system and its air filter are just as unique. If you aren’t sure when to replace the filter and want to know more, just call us at River Valley Air Conditioning.

The General Rule of Thumb


When you’re looking for how often to change air filters in HVAC, you’ll easily come across an answer; once every 90 days or two months. This is considering that you live in the home with the HVAC system in question and don’t move between homes frequently. 

However, this is just a general idea of the expected time frame. Many other factors can influence the time and make it longer or shorter. However, in general, it’s good to check your air filter once at the end of each season, since your HVAC air filter is what’s responsible for cleaning your home’s air. Doing so ensures that your HVAC system works efficiently and avoids overheating and reduced efficiency.

If you aren’t sure of how often to change your air filter HVAC, regularly checking the filter can narrow down when it needs replacing. The tip can be especially useful for homes and families that frequently have the number of occupants growing and shrinking multiple times throughout the year!

Air Conditioner Filters vs. Furnace Filters

The HVAC system is one possible factor that can change how often you need to replace the air filters. 

When they’re used, air conditioners and furnace air filters see different amounts of dirt and debris. With cold weather and snow being the most common debris, furnaces can usually go for much longer between filter replacements. Soil and sand can still be a big issue, especially during Arizona winters. As a result, try replacing the furnace air filter once a month to once a season, depending on your winter weather.

On the other hand, air conditioners see far more sand and other debris due to how dry the summer months tend to be. How often to change an HVAC filter can become much shorter when considering everything the filter needs to clean out. With all the dirt, an AC’s air filter gets dirtier faster and should be replaced about once a month.

Thicker Air Filters vs. Thinner Filters

If you’ve ever checked your HVAC system’s air filter before, you might have noticed that there’s a certain thickness rating on it. Typically found on pleated air filters, the overall thickness of it can be anywhere from an inch thick to five or six inches. This measurement can be one of the best ways to tell how often to change your HVAC air filter. 

The natural thing about an HVAC air filter’s thickness is that a six-inch thick pleated filter will be able to clean the air passing through far more efficiently than a thinner one. However, this means that the thinner the air filter, the faster it gets dirtier and needs to be replaced.

Once you know the ideal inch thickness needed for your HVAC system, narrowing down the specific time when you need to replace it becomes easier. These are just rough estimates, though, and may change depending on the weather.

  • 1” pleated filters – once every 30 to 60 days
  • 2” pleated filters – once every 3 months
  • 3” pleated filters – once every 120 days
  • 4” pleated filters – once every 6 months
  • 5” or 6” pleated filters – once every 9 to 12 months

Do Different Kinds of Air Filters Change the Time Range?

Senior caucasian man changing a folded air filter in the HVAC furnace system in basement of home

One key difference between air filters is their type. Like an HVAC system, each air filter can be one of many different types, each cleaning the air’s contaminants in different ways. Similarly, each filter can be cleaned in different ways, and you might not have to buy a new air filter every time. 

Fiberglass air filters are quite inexpensive to buy compared to some of the other varieties, making the fact that they’re disposable far easier for many homeowners to handle. Due to how they’re made, the HVAC system has a much easier time drawing in air. However, it only filters out larger particles, requiring these filters to be replaced once a month or less.

Another type, the HEPA filter, is also designed to be far more effective at filtering air than most others. Also referred to as a high-efficiency particulate air filter, these are the ones you need to get if you or your family has allergies. 

While they are more expensive than fiberglass, HEPA filter get rid of nearly all the contaminants in the air and are often thicker. If you have a HEPA filter installed, you can go for nearly a year before replacing it!

Finally, another important thing that can differentiate air filters and how often to change an HVAC filter is whether it’s washable. Some air filters, like electrostatic ones, are considered reusable instead of disposable. 

While they tend to be less efficient at filtering air, they still are efficient enough for families without allergies. Needing to wash them once a month also means that you can easily set aside a few hours.

Factors That Affect When to Change the Air Filter

Of course, a few other factors also need to be considered when looking when you need to replace your air filter. The number of people that live in your home is one, on top of whether you have any pets. If you have more people and pets in your household, you’ll need to change the filter more often. In some cases, a home with two to three pets and a family with children needs a new filter about every 20 to 45 days.

The size of your home can also impact how often you need to change it. Larger homes often have far more air circling through them and need more warm or cool air to reach set temperatures. With that much air moving through the air conditioner or furnace, much more debris gets sucked in as well. This, naturally, results in needing replacements more often.

And, as mentioned, allergies often play a big role in changing – and even choosing – air filters. Since it’s hard to tell exactly what allergens are in the air your HVAC system blows out, having a good air filter is important. 

Even minor seasonal allergies are already quite troubling to deal with whenever you go outside, so it’s only natural that you want guaranteed clean air in your home. Replacing an air filter earlier than expected can help a lot for some.


Air filters are vital to keeping our home’s air quality as high as possible. Since the filters are what cleans the air, they can become quite dirty with enough time. To ensure both HVAC system efficiency and clean air, you must regularly replace the air filter. However, when you need to do so depends on a few key factors we’ve mentioned.

So, if you need help with any HVAC-related work, air filter or not, our River Valley Air Conditioning team is here to help!