Why You Should Change Your Air Filter Every 3 Months (90 Days)

Replacing the filter in your air conditioning and/or heating system regularly keeps your appliances working properly and your energy bills low. It's also a task that many homeowners forget about for months at a time, which can send your energy bill skyward and potentially contribute to other maintenance issues down the line. Read on to find out the best rate at which to change your air filter!

General Recommendations

So, how frequently should you change your air filter? The answers is: it depends.
Typical recommendations range from every 30 days for cheaper fiberglass filters (which often don't do a great job of filtering), to as long as 6 months for higher-end pleated filters. These estimates assume average use and take into account the type and size of your filter.

A general rule of thumb for pleated air filters (like ones made by FilterBuy) is to replace your filter every 90 days. As your filter traps more dirt, dust, and allergens from the air, filter efficiency decreases. Find out below if you should be replacing your filter more often.

a fresh air filter blocks unwanted particles while allowing clean air to flow through

Does someone in your home have asthma and/or allergies?

Those with asthma and/or allergies are much more sensitive to airborne particles than those without. If you have an asthma- or allergy-sufferer at home, change your filter every 6 weeks to ensure indoor air quality is at its best.

Do you have pets?

Cats and dogs shed and have odors that can build up in your space, making it necessary to change your filter every 2 months. Generally, cats and dogs shed most when winter turns to spring and summer turns to fall, which are key times to replace your filter.

ac units require consistent maintenance to ensure longevity and cooling power

Do you have young children?

Superior indoor air quality is especially important with kids around. Keep your home clean and air quality under control by replacing your vacuum filter every 2-3 months.

Factors that can affect your HVAC air filter's lifespan include:

Image of an HVAC mechanic standing next to an AC unit

The rate at which you use your heating and/or cooling system

If you live in a temperate climate and use your heater and/or air conditioner up to a few hours every day, a single filter can last you from a whole season to an entire year. If your HVAC system is running on a near-constant basis, however, change your filter every few weeks (especially if you're using a cheaper fiberglass filter).

The size of your home

Furnaces and air conditioners in smaller homes need to pump less air for the same amount of temperature change, which may mean less frequent filter changes. These appliances are often built with smaller filters, though, and thus may need to be changed just as regularly as a filter in a larger home.

graphic of a house
air filters impact air quality and airflow in your home

The air quality within your home

The air within or outside your home will also affect your filter's replacement cycle. Pets or poor air quality, for example, will require you to replace your air filter more frequently.

How to Tell When Your HVAC Air Filter Needs Changing

Any use will lead to some amount of dirt being trapped in your air filter - that's its job, after all.
So how do you know when your filter has trapped too much dirt and needs to be replaced?

Repair Man Image

There's no strict guideline, but if your filter shows only a subtle layer of dirt under which the filter's material is still visible, your filter is in fine working order. Once it gets much beyond that point, it's ready to be changed out. If there's a visible coating of dirt covering most of your filter's surface that is adequately thick to obscure the filter material itself, that's a sign that your filter has been in your HVAC system far too long.

Every few weeks, take out your filter and give it a look! Is there a musty odor? Is the filter covered in dust? If in doubt, it's always best to err on the side of replacing your filter. They're relatively inexpensive, and that small cost to keep your heating and cooling vents clear will be well worthwhile when your energy bill comes due. If it's been a while since you've changed your filters, we can help you find the right size, brand, and type of HVAC air filter for your furnace and/or air conditioner.

Ready to replace your filter? Click here and get your system back to clean efficiency!

How Often Do I REALLY Need to Change My Air Filter?


How do I know if my air filter needs changing?

There are often obvious signs that your air filter needs changing. They include:

  • Dust and debris accumulating on your intake vents
  • Dust and debris accumulating near your output vents, often on the ceiling and walls nearby
  • Dust accumulating on fan blades, curtain rods, on top of cabinets, indicating that there is an excess of dust in circulation
  • Noticeable loss of cooling power in your AC system
  • Sounds of excessive strain when your AC system starts up
  • Longer periods of run time for your AC system to cool to desired temperature
  • Indicator on your AC controls telling you to change your air filter

When in doubt, buy a replacement air filter and change it out.

How long can you go without changing the air filter?

The longest you should go without changing your air filter is the recommended 90 days. However, if replacing your air filter is simply out of the question for an extended period of time, going beyond 90 days is not going to cause irreparable harm to your AC system. However, you will put unwanted strain on your HVAC system, resulting in poor air quality and air circulation.

What are the symptoms of a dirty air filter?

Symptoms of a dirty air filter can include:

  • Dust and debris accumulating on your intake vents
  • Dust and debris accumulating near your output vents, often on the ceiling and walls nearby
  • Dust accumulating on fan blades, curtain rods, and on top of cabinets, indicating that there is an excess of dust in circulation
  • Noticeable loss of cooling power in your AC system
  • Sounds of excessive strain when your AC system starts up
  • Longer periods of run time for your AC system to cool to desired temperature

Does changing the air filter make a difference?

Yes, changing your filter has several impacts on your HVAC system’s ability to cool your house and the overall quality of your air. When you change your air filter, you allow more air to flow through your system with less power usage resulting in better circulation, cleaner air, and a lower electricity bill.

How often do you need to change your AC filter?

It is recommended to change your AC filter every 1 to 3 months, depending on factors such as the type of filter, the level of usage, and the presence of pets or allergies in the home. Regularly changing the AC filter helps maintain indoor air quality, improve efficiency, and prolong the lifespan of your HVAC system.

What happens if the HVAC filter is not changed?

If the HVAC filter is not changed regularly, it can lead to various issues. A clogged or dirty filter restricts airflow, causing the system to work harder and consume more energy. This can result in higher energy bills, reduced efficiency, increased wear and tear on the system, and potentially even system breakdown. Moreover, poor indoor air quality can result from the accumulation of dust, allergens, and contaminants in the air.

Do you need to change the furnace filter every 3 months?

Yes, it is generally recommended to change the furnace filter every 3 months. However, this frequency can vary based on factors such as the type of filter, the presence of pets, and indoor air quality concerns. Regularly changing the furnace filter helps maintain efficient operation, prevent system issues, and ensure clean air circulation throughout the home.

READ MORE: How Often Should You Change Your Furnace Filter

How do I know when my HVAC air filter needs to be replaced?

You can determine when your HVAC air filter needs to be replaced by inspecting it regularly. Signs that indicate a filter change is needed include visible dirt and debris buildup, reduced airflow from vents, an increase in dust around the home, and a decrease in system efficiency. Additionally, some filters come with indicators that change color when it's time for a replacement.

Do I need to change my air filter every month?

While changing the air filter every month may not always be necessary, it can be beneficial in certain situations. Homes with pets, smokers, or allergies may require more frequent filter changes to maintain indoor air quality. Additionally, high-usage households or homes in dusty environments may benefit from monthly filter changes to prevent clogs and maintain system efficiency.

Why is my air filter black after one week?

A black air filter after one week indicates heavy contamination and a high level of pollutants circulating in your home. This could be due to factors such as smoking indoors, pets shedding excessively, nearby construction, or poor indoor air quality. Regularly changing the filter and addressing underlying air quality issues is crucial to prevent health risks and maintain system efficiency.

How long can an AC go without a filter?

An AC unit should not operate without a filter in place. Running an AC unit without a filter can lead to serious issues such as dust and debris buildup on the evaporator coil, reduced airflow, decreased efficiency, and potential damage to the system. It is essential to always have a clean filter in place to protect your AC unit and maintain indoor air quality.

How long can an HVAC filter last?

The lifespan of an HVAC filter can vary depending on factors such as the type of filter, the level of usage, and the indoor air quality. Standard HVAC filters typically last between 1 to 3 months, while higher efficiency filters may have a longer lifespan. Regularly checking and replacing the filter as needed is essential to ensure optimal system performance.

How long can you go without changing the furnace filter?

It is not recommended to go without changing the furnace filter for an extended period. A dirty or clogged filter can lead to reduced system efficiency, increased energy consumption, poor indoor air quality, and potential damage to the furnace. Regularly changing the furnace filter every 3 months or as needed is essential to maintain a healthy and efficient heating system.

Do I need to change my furnace filter if it doesn't look dirty?

Even if the furnace filter does not appear visibly dirty, it is still important to follow the recommended replacement schedule. Over time, filters can become clogged with microscopic particles that are not readily visible. Regularly changing the filter helps ensure proper airflow, efficient operation, and clean air circulation even if the filter does not look dirty.

Why is my furnace filter so dirty every month?

A furnace filter becoming dirty every month can be attributed to various factors such as high levels of dust and debris in the home, pet hair, smoking indoors, or poor air quality. Additionally, a filter that becomes dirty quickly may indicate that it is not the right type or efficiency level for your home's needs. Addressing underlying air quality concerns and using the appropriate filter can help reduce the frequency of replacements.

What MERV rating do I need for the home?

The MERV (Minimum Efficiency Reporting Value) rating needed for your home depends on factors such as indoor air quality concerns, allergies, pets, and HVAC system compatibility. For most homes, a MERV rating between 8 and 11 is recommended to strike a balance between effective filtration and system efficiency. However, homes with specific air quality requirements may benefit from higher MERV-rated filters, but it is important to ensure compatibility with your HVAC system.