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Most HVAC filters, including furnace filters, should be changed every three months.
Inspect your HVAC filters once per month to see if you need to change them.
Filters that are only 1 or 2 inches thin need to be changed more frequently than thicker filters.
Choose filters with a higher MERV rating to reduce the frequency of changing filters.
Plan to spend $10 to $50 on average for HVAC filter replacements.
Your HVAC system is one of the most important parts of your home, working to keep your family warm in the winter and cool in the summer. But it can only do so when it has clean, dust-free filters. So, how often should you change your furnace filters and AC filters? Grab your calendar and a pen, and let’s find out.
Most HVAC systems work best when you change the filter once every three months. However, your home’s size, the number and type of pets you have, allergy sensitivities, and filter thickness will impact how often you should change furnace filters and AC filters. No matter what filter you have or the square footage of your home, inspect the HVAC filter at least once per month to determine if you need to change it early.
HVAC filters aren’t bound to a set changing schedule. From the type and size of filter your furnace uses to your home size and household habits, many factors will influence how often you should change the HVAC filters.
Thicker air filters can go longer between changes than thinner air filters. You can find the size of your filter listed on the side of the filter. You’ll see three numbers that define the width, length, and depth (in that order).
Here’s how often to change HVAC filters based on their size:
| Size (Inches) | How Often to Change |
|---|---|
| 12x20x1 | 1–3 months |
| 14x18x1 | 1–3 months |
| 20x20x1 | 1–3 months |
| 20x25x2 | 1–3 months |
| 16x25x4 | 6–9 months |
| 16x25x5 | 9–12 months |
There are many different types of furnace filters and AC filters you may want to consider for your system, but make sure the option you choose is compatible with your household HVAC. Some options, like washable filters, need to be changed frequently but are easy to wash and reuse. Other options, like HEPA filters, cost more upfront but only need to be switched out once or twice per year.
Based on the filter type, here’s how often to change your HVAC filter:
| Type | How Often to Change |
|---|---|
| Flat | 1 month |
| Washable | 1 month |
| Fiberglass | 1–2 months |
| Polyester | 1–3 months |
| Pleated | 2–4 months |
| Media | 6 months |
| HEPA | 12 months |
The larger your home is, the more often you’ll need to change the HVAC filters. That’s because more air is passing through the HVAC system, and the air has to condition more square footage. Larger homes also tend to have more household members. More members of the household means there are more people tracking in dirt or shedding skin cells, all of which can contribute to a shorter filter life span compared to a smaller home with only one or two household members.
The way you and your family go about your daily lives at home can make a difference in how long your HVAC filters last. From cracking open a window at the first sign of spring to running the heater fan when the winter chill sets in, the following household habits can also impact how often you’ll need to change your HVAC filters.
Opening doors and windows: Fresh breezes also bring in dust, dirt, pollen, and other outdoor contaminants. If you keep windows open often, change the filters once per month.
Smoking: Smoking is a major factor in how often to change HVAC filters. If you or any members of your household smoke, you should change thinner filters at least once per month, and you should change even 6-inch filters every three months.
Running the heater fan: Keeping the heater fan on may feel cozy, but it also wears out the filter and other HVAC parts. Change filters once per month if the heater fan runs often.
Owning pets: We all love our furry friends, but shedding and pet dander mean you’ll need to change HVAC filters more frequently, about every two months.
There are many reasons to change your HVAC filters, especially if you like saving money and spending less time on chores. Not only that, but running a furnace without a filter or turning on the AC with no filter or an old filter can actually damage your HVAC system.
Here are just some of the benefits of keeping up with this important chore:
Reduce allergies: You can keep allergies and poor air quality at bay by using filters with higher MERV (minimum efficiency reporting value) ratings.
Clean less: By changing the air filters, the filters will capture more dust and debris rather than letting it circulate in the air throughout your home.
Lower your energy bills: Clean HVAC filters allow the system to run more efficiently. This means the HVAC system will use less energy to operate, saving you money on your utilities.
Spend less on repairs: Dirty air filters cause the HVAC system to work harder, and this wears out its parts faster. Replacing air filters can extend the life of your HVAC system.
If you’ve moved into a new house or didn’t realize you should be changing the HVAC filters frequently, don’t worry. There are plenty of signs to watch for that will let you know it’s time to swap the filter.
Dirty filter: If the filter is visibly dirty or caked with dust, replace it.
Dust everywhere: If you notice that dust is building more quickly than ever, you may need to change your HVAC filter more often.
Frequent running: If you’re running your system more often, say in the hottest parts of summer or the chilliest parts of winter, you need to change HVAC filters more often, too.
Unpleasant odors: If your furnace or HVAC system smells weird or always smells like it’s burning (aside from the first few times you turn it on during winter), an old filter could be the cause.
Higher energy bills: If your heating and cooling bills are higher than usual, that indicates the system isn’t working efficiently. It could be a dirty filter or other broken parts.
Incorrect temperature: If your vents are blowing cool air with the furnace on or hot air when the AC is on, the dusty filter may be preventing the HVAC from working correctly.
Luckily, even novice DIYers can learn how to replace an AC filter or how to change out a furnace filter. HVAC filter replacements cost $10 to $50, depending on the type of filter.
However, if you seem to be cycling through filters faster than normal or you have other concerns about changing the filters or your HVAC system’s health, hire a local furnace company to inspect the HVAC and change the filter. Hiring a pro will add around $50 to $150 per hour to the cost of the filter replacement.
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