Find Compatible Filters for the Following Brands
- AAF Air Filters
- 3M Filtrete Air Filters
- Abatement Technologies
- Accumulair Air Filters
- Ace Air Filters
- Trion Air Bear® Compatible Air Filters
- Air Demon Air Filters
- Air Guard Air Filters
- AIRx Air Filters
- Replacements for AllergyZone Air Filters
- Amana Air Filters
- AmericanAirFilter Air Filters
- American Standard Air Filters
- AprilAire Air Filters
- Arm & Hammer Air Filters
- BestAirPro Air Filters
- Broan/NuTone Air Filters
- Bryant Air Filters
- Carrier Air Filters
- ClimateMaster Air Filters
- Coleman Air Filters
- Dynamic Air Cleaner Refills
- DuPont Air Filters
- Electro-Air Air Filters
- Endust Air Filters
- Field Controls Filters
- Five Seasons Air Filters
- Febreze Air Filters
- Flanders Air Filters
- GeneralAire Air Filters
- Glasfloss Compatible Air Filters
- Goodman Air Filters
- Indigo Air Filters
- Honeywell Filters
- Honeywell Air Filters
- NordicPure Air Filters
- Lennox Air Filters
- Lysol Air Filters
- Payne Air Filters
- Nordyne Air Filters
- Permatron Air Filters
- PrecisionAire Air Filters
- Pro1 IAQ Air Filters
- PuraFilter 2000 Air Filters
- Purolator Air Filters
- ReservePro Air Filters
- Rheem Air Filters
- Ruud Air Filters
- Skuttle Media Filters
- SafeHome Air Filters
- Space-Gard Air Filters
- TopTech Air Filters
- Totaline Air Filters
- True Blue Air Filters
- WaterFurnace Air Filters
- Trane Air Filters
- Ultravation Air Filters
- White Rodgers Air Filters
- York Air Filters
Don't see your brand listed?
Contact us to help find your filter.
21x21x1 Air Filters
WHY YOU SHOULD REPLACE YOUR AIR FILTER
Reduce your energy costs with clean filters
A dirty filter in your furnace or AC system will raise your energy bills. A dirty filter restricts the air flow into your system's air handler, causing it to work harder to cool or heat your home.
Improve airflow & efficiency of your furnace
A dirty clogged filter can restrict furnace or AC airflow and potentially cause problems with the system. They also cease to filter allergens and other particulates out of your air.
Increase the longevity of your furnace or AC system
Dirty, unchanged filters can make your furnace or AC system fail completely. Repairing a broken system can end up costing you a pretty penny.
WHAT DO MERV RATINGS MEAN?
Allergies, pets, odors and smoking all can greatly affect the quality of your indoor air. Discount Filters offers many different types of discount air filters to help you breathe better air inside your home based on your specific needs.
We carry discount air filters in 1-2 inch standard sizes, and 3-5 inch media sizes. Our air filters are great and work well in HVAC systems, furnace and air conditioner systems. If you are looking for a custom size air filter you can request that we make a special size for you. As always, we offer Fast Shipping & Free Returns on all of our discount furnace filters.
- MERV 8: The most basic air filter a homeowner will need is a MERV 8. A MERV 8 filter offers excellent air filtration for their home. A MERV 8 air filter would be good for a family that doesn't smoke, doesn't have pets, and doesn't have bad allergies.
- MERV 11: People with pets and/or light allergies, would greatly benefit from a more advanced filtration level called a MERV 11. A MERV 11 filter reduces pet dander, dust, pollen and other particles that are present in your home.
- MERV 13: A MERV 13 air filter however will capture even smaller dust particles, dirt, pollen, mold spores, pet dander and more from your home's air. A MERV 13 air filter is great for people with regular allergies and who own multiple pets. The MERV 13 filter is typically more expensive and will also put more strain on your HVAC system, however the high quality filtration you will get will be well worth it.
Frequently Asked Questions
I'm looking for a 21x21x1 filter for my furnace - will an air conditioning filter work?
Depending on where you live, you might refer to the filter one way or the other. The good news is - it doesn't really matter. All forced air heating/cooling systems use a filter - which serves to keep your equipment clean and to promote good indoor air quality in your home.
How often should I change my furnace / air conditioner filters?
It's important to change your 21x21x1 air filter to keep your heating and/or cooling system operating at peak efficiency. There are general guidelines for filter change intervals: Replace 1" fiberglass/polyester filters every 30 days. Replace 1" and 2" pleated filters every 90 days. Replace 4"-5" filters every 6 months.
What is an HVAC filter?
HVAC stands for Heating Ventilation and Air Conditioning. "HVAC system" refers to the system that regulates (heats/cools) and moves air throughout your home. In addition to keeping your HVAC system clean, your filter removes airborne particles and allergens from the air in your home.
How do I choose my whole house air filters?
The industry standard for rating the efficiency of air filters is "MERV", which stands for Minimum Efficiency Reporting Value. Manufacturers and retailers have attempted to simplify things by creating different comparison systems. Examples: FPR (Filter Performance Rating), or MPR (Micro Particle Rating), or even a good/better/best/ultimate system. At DiscountFilters.com - we organize our filters into different categories - "Dust", "Allergy", "Health" and "Odor". We provide information on the common contaminants that each filter category removes on our product pages.
How do I know what air filter to purchase?
The first things to consider when looking for an air filter are dimensions. Most air filters will have dimensions printed on the side of the filter frame. The "nominal size" is the size you see printed on the filter; it originates from the actual size, which is rounded up to the nearest whole inch.
What 21x21x1 air filters do you recommend for my furnace and/or air conditioning system?
We carry a huge selection of filters in many different sizes. We stock many more sizes than the local "big box" or hardware store. In most of the common sizes - we might have 5 different choices ranging in price and efficiency. We recommend the AIRx "Allergy" filters (MERV 11) as these offer the best combination of performance and value.