One of the simplest and most affordable ways to keep your HVAC system running smoothly is to change the air filter regularly. Replacing dirty AC and furnace filters keeps harmful air particles from clogging up your heating and cooling system. It also allows proper airflow through the system, preventing premature wear on the equipment.
How often should AC filters be changed? That depends on several factors, such as the size and type of air filter you use, the MERV rating, and your HVAC system’s manufacturer specifications. Below, we take a look at these factors and provide a comprehensive guide on how often you should change your AC or furnace filter. If you have further questions, feel free to contact Discount Filters.
How Do I Know If My AC Air Filter Needs Replacing
In most cases, replacing the air filter is necessary every 30 to 90 days. However, there are other symptoms that indicate you should replace your dirty filter. Let’s look at some of the more common signs you need to replace your air filter.
| Visible dirt and dust | If you can see dirt, dust, or debris on the filter surface, it’s time for a replacement. A clean filter should appear white or off-white. |
| Increased energy bills | A clogged filter makes your HVAC system work harder. It leads to higher energy usage and utility bills. |
| Poor air flow | If you notice weak airflow from vents, it could be a blocked filter restricting air movement through the system. |
| More dust in your home | A dirty filter allows more dust to circulate. You’ll notice more dust in every room in your house. |
| Allergies or respiratory issues | If you or family members experience more allergy symptoms or respiratory problems, it might be a dirty filter not trapping the particles like it should |
| Unusual HVAC noises | A clogged filter can cause your HVAC system to work harder. You may hear strange noises like whistling or humming. |
| Moldy or musty smells | If you detect unpleasant odors from your vents, it could be mold growth on a damp, dirty filter. |
| The filter has been in use for 3+ months. | Most filters should be replaced every 1-3 months, depending on usage and other factors in your home. If it’s been more than 90 days, you need to change the filter. |
How Long Should an AC Filter Last?
How do I know if my AC filter needs replacing? The average AC filter lifespan is 30 to 90 days, depending on four main factors:
- Type/style (material)
- Brand
- Size
- MERV rating
However, there are external factors that determine filter longevity and how often you should replace the AC filter:
What is the Household Size?
The number of people living in your home directly impacts how quickly your AC filter becomes dirty. A study by the National Air Filtration Association found that households with more occupants need to change HVAC filters 30-50% more frequently. For instance, a single-person household might change its filter every three months, while a family of four may need to change it every 1-2 months.
How are the Pollution Levels?
The EPA reports that indoor air can be 2-5 times more polluted than outdoor air. Homes in urban areas or near industrial zones may need filter changes up to twice as often as rural homes. High pollen counts, wildfire smoke, or construction dust can reduce filter life by 25-40%.
What are the HVAC Equipment Requirements?
Your HVAC system’s specifications play a crucial role in determining filter lifespan. Most manufacturers recommend changing 1-inch filters every 1-3 months. However, thicker HVAC filters (4-5 inches) can last up to 6-12 months. Energy Star suggests that systems running more than six months per year need more frequent filter changes. Regular maintenance can extend filter life by 15-20%.
What is the Difference Between Apartments vs. Houses?
If you live in an apartment, change your air filter every 60-90 days due to smaller living spaces and less air circulation. If you live in a home, you may need to replace the filter more frequently, depending on factors such as your house size and occupancy. Both apartment residents and homeowners with pets or allergies should consider changing filters more often, approximately every 20-45 days, for better air quality.
What is the Difference Between Urban vs. Rural Areas
If you live in an urban area, you should change your HVAC air filter every 30-60 days due to higher pollution levels. If you live in a rural area, you can often extend filter changes to every 60-90 days. However, you should always check your filter monthly and replace it sooner if it appears dirty or clogged.
What Happens When You Don’t Change the AC Filter?
The consequences of not changing your AC filter can be costly—both short-term and long-term costs.
| Poor HVAC efficiency | Your HVAC system has to work harder to push air through a dirty filter. As a result, the filter reduces its efficiency. You’ll notice less consistent heating or cooling throughout your home. |
| Decreased airflow | A clogged filter restricts airflow, making it harder for your system to circulate air effectively. You may feel weak air coming from your vents, which causes an imbalance in temperature throughout the house. |
| Increased utility bills | As your system struggles to maintain your desired temperature, it runs longer and uses more energy. You’ll see a noticeable increase in your monthly energy costs. |
| Premature system breakdowns | The extra strain on your HVAC system can cause the equipment to wear out faster. You can expect premature breakdowns and a shorter lifespan from your AC or furnace. |
| Expensive repairs | A dirty filter affects your HVAC and can lead to serious issues like frozen coils or damaged motors. You may face costly repairs or frequent AC maintenance that could have been avoided with regular filter replacement. |
Do You Really Need To Change Air Filters Every 3 Months?
As we mentioned earlier, general guidelines suggest that you keep a tight air filter schedule, changing filters at most every three months. However, the 3-month rule may not apply to your lifestyle or home environment.
Below are some examples where changing air filters sooner than 90-day intervals may be a smarter option:
| I have pets | Every 30-60 days. More frequent for multiple pets or long-haired breeds. |
| I’m a smoker. | Every 30-45 days. Smoke particles quickly clog filters and reduce air quality. |
| I have allergies | Every 20-45 days. More frequent changes help reduce allergens in your home. |
| The air in my home is dirty. | Every 30-60 days. Consider more frequent changes if you notice visible dust accumulation. |
| I have an older HVAC system. | Every 30-60 days. Older systems may be less efficient and benefit from fresh filters. |
Special Considerations for Specific Settings
Different filters, washable filters, purifiers, and environments may require unique filter replacement schedules that don’t fall into standard requirements. Let’s take a look at a few examples below:
How often do I replace the air filter in my car cabin?
Change the air filter in your car cabin every 15,000 to 30,000 miles or at least once a year. Check your vehicle’s owner manual for the manufacturer’s specific recommendation. You may need to replace it more frequently if you drive in dusty conditions or heavily polluted areas.
How often do I change my air filter with pets?
If you have pets in your home, change your HVAC air filter every 30 to 60 days. Replace it more frequently if you have multiple pets or long-haired breeds that shed a lot. Check your filter monthly and change it sooner if it appears dirty or clogged with pet hair and dander.
How often do I change my air filter in an apartment?
Replace your HVAC air filter in an apartment every 60 to 90 days. Check your filter monthly and replace it sooner if it looks dirty or clogged. Adjust your replacement schedule based on factors like pets, allergies, or indoor air quality.
How often do I change the air filter in my air purifier?
Check your manufacturer’s recommendations for specific guidance on your model. Otherwise, change the air filter in your air purifier every three to six months. Replace the filter more frequently if you run your air purifier constantly or live in an area with high pollution levels.
How often do I change a 20x25x4 air filter?
Replace your 20x25x4 air filter every six to 12 months. Check your filter every three months and replace it sooner if it appears dirty or clogged. Adjust your replacement schedule based on factors like pets, allergies, or local air pollution levels.
Buy Quality Air Filters Online From Discount Filters
Although it’s important to change your filters as needed, the first step in achieving indoor air quality is investing in high-quality, dependable fillers. Discount Filters can help you create a cleaner, healthier home environment with our selection of brand-name AC and furnace filters. Got questions? Contact one of our filter experts via live chat or call our toll-free number.