How Often Should You Change Your Air Filter?

Your air filter is designed to improve your home’s air quality and protect your heating, ventilation, and air conditioning (HVAC) system. Over time, the filter can become loaded with dust, allergens, and other particles. Once this occurs, it must be replaced.

When it comes to how often to change an air filter, the general rule of thumb is not the best option for our region. Instead, we’ll take a look at replacement schedules based on your filter type, when filters should be changed early, and why timely replacements are necessary.

Why “Every 90 Days” Is Not a Real Answer

Whenever you’ve opened an air filter in the past, you’ve probably noticed that it says to change your filter every 90 days. In reality, the 90-day figure is a starting point and not the most accurate answer. This 90-day figure assumes an average household, with an average climate, and an average level of use. The problem is that very few homes are perfectly average in all three areas.

Your air filter replacement schedule will vary based on your filter thickness, household conditions, season, and air quality. Once you’ve figured out a basic schedule, there is a simple way you can check to see if your filter needs to be replaced early.

Filter Thickness Changes Everything

So, how often should I change my AC filter? The answer heavily involves your filter thickness. A thicker filter is capable of holding more material before airflow suffers, so you can stretch the intervals between changes. You must determine which filter type you have before you set up a replacement schedule.

1-Inch Disposable Filters: 30 to 90 Days

These filters should generally be replaced every 30 to 90 days, but replacements should occur more frequently during periods of peak use. In Fort Collins, you’ll need to check for signs of a dirty air filter monthly.

4-Inch and 5-Inch Media Filters: 6 to 12 Months

At a minimum, you should replace a 4-inch media filter every 6 to 9 months. A 5-inch filter should be changed every 9 to 12 months.

What Actually Speeds Up Filter Loading

Two identical homes on the exact same street can end up requiring very different filter replacement intervals based on the following factors.

• Pets: This is especially true if you have heavy shedders or multiple animals.
• Household Size and Activity: Increased foot traffic means there is more dust in the air.
• Smoke Season: When smoke season arrives, indoor air quality (IAQ) can decline as fine particulates end up indoors. 
• Construction and Renovations: New construction, like homes in the growth corridor, loads filters faster because of the added dust. 
• Allergies or Respiratory Issues: While your family’s allergies will not make the filter load faster, they will affect how frequently you need to replace it. Especially during peak allergy season, more frequent filter changes may be necessary to keep your family comfortable.
• Continuous Fan Operation: If you run the fan continuously instead of setting it to auto, the filter will need to be changed more often.
• Dry, Dusty Conditions and Wind Events: Northern Colorado’s climate can shorten baseline replacement intervals for local HVAC systems.

In Fort Collins and Loveland, our climate and local conditions mean that we tend to fall on the shorter end of published intervals.

A Seasonal Schedule That Fits Northern Colorado

The right filter change interval changes throughout the year, which is one reason why filters are so frequently changed at the wrong time.

Summer

During summertime in Northern Colorado, our systems run long cooling cycles each day. As fine particulates from wildfire smoke and haze move into the region, the filters become loaded much faster than they do during the rest of the year. Because of this, filters should be checked monthly.

Fall

Fall is the transition point. It is a practical moment for changing your filter before the heating season begins.

Winter

In winter, homes in Loveland and Fort Collins are often closed up. The same air is recirculated and heated, leading to dry indoor conditions that keep dust airborne longer. How often you need to change the furnace filter will be impacted by how intensely the furnace is used during our cold stretches.

Spring

During springtime, the Front Range experiences grass pollen, cottonwood pollen, and wind events that can clog air filters. Because of the added allergens and dust in the air, monthly filter checks are necessary.

No matter what season it is, you can easily determine if a new filter is needed by holding it up to light. If light won’t pass through the filter easily, it needs to be replaced. When you install the new filter, you should always write the date on it so that you can easily track when the next replacement is needed.

What a Dirty Filter Actually Costs You

Changing your air filter in Fort Collins isn’t just a housekeeping chore. It’s an important task for boosting your comfort, energy efficiency, and performance.

• Comfort: When airflow is restricted, your rooms receive less conditioned air. The far end of your home may struggle to cool off as quickly as the rest of the house.
• Operating Cost: Dirty filters force the system to run longer to reach the same temperature.
• Frozen Evaporator Coil: A dirty filter prevents air from flowing across the evaporator coil. Because this coil is designed to absorb heat, poor airflow can result in the coil icing up.
• Short Cycling: In heating mode, restricted airflow can cause overheating and safety shutdowns. 
• Equipment Strain: Over time, the blower must work against the added resistance. This increased wear can eventually lead to premature breakdowns and repairs.
• Indoor Air Quality: A loaded filter cannot do the job it is made for, so your home’s IAQ can suffer.

Choosing the Right Filter, Not the Highest Rated One

If you’ve ever wondered “What MERV rating should I use?”, you’re not alone. The MERV rating represents how effectively a filter captures airborne particles of specific sizes. A higher MERV rating means it is better at removing contaminants. 

Although it might intuitively seem that a higher MERV rating is always better, this is not the case. A denser filter restricts airflow more, which can be an issue if your system is not designed to handle it. The right filtration level balances your equipment’s abilities with your filtration needs. 

Most homes benefit from having a mid-range MERV rating. However, you should talk to your HVAC technician about your options if anyone in your home has allergies.

FAQs

For a deep dive into AC filters and airflow, check out some of our most frequently asked questions.

How often should I change a one-inch filter? 

How often to change the air filter is different in Northern Colorado. While the filter’s package might recommend 30 to 90 days, the real figure is closer to 30 days in our area. Ideally, you should check your filter at least once per month.

Do I need to change the filter in winter, too? 

Yes, you should change the filter in winter as well. In most Northern Colorado homes, heating and cooling systems share the same filter. Make sure to change the filter as part of your pre-winter checklist. Then, check it monthly to see if it needs to be replaced.

Can a dirty filter stop my AC from cooling?

It can. When the filter is dirty, it restricts airflow. This can result in poor cooling performance and a frozen coil.

Is a higher MERV rating always better? 

Not always. A denser filter will restrict airflow, which can cause added wear on a system that is not designed to handle it.

Does a washable filter work as well? 

Although washable filters can reduce waste, they are generally less effective at filtering fine particulates. Additionally, they must be completely dry before they are reinstalled.

What if I forgot when I last changed it? 

If you cannot remember when you last replaced the filter, go ahead and change it now. Then, write the date on the new filter frame so that it is easy to remember next time.

Optimize Your Home’s Airflow

Unsure how often to change your air filter? If you’re experiencing airflow issues in the Fort Collins or Loveland area, Balance Point Heating, Cooling & Plumbing offers the maintenance visits and upfront pricing you need.

As a Whole Home Comfort Plan member, you can take advantage of scheduled maintenance visits. We’ll make sure your filter and system are properly cared for, so you can enjoy a better level of comfort and energy efficiency.