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The best air filter for a Lennox air conditioner is one that matches the filter size, depth, and type specified for your particular installation. Lennox does not use one universal filter size across its systems. Check the filter already installed and your equipment manual before buying; if the filter or housing is unclear, ask a Lennox dealer.
How to find the right Lennox air-filter size
Start with the filter currently installed. Lennox says filters may sit in a return-air vent on a wall or ceiling, beside the furnace or air handler, or inside the unit behind an access panel. Turn the system off before accessing the filter, and follow the equipment manual’s instructions for opening any panel.
- Read the existing filter label. Note its printed dimensions and type, including depth. Use those details to find a replacement rather than assuming a size based on the Lennox brand.
- If there is no filter, measure the opening. Check the furnace or air-handler manual for the specified size and type. The opening alone may not establish which filter the system requires.
- Confirm compatibility if anything is uncertain. Contact a local Lennox dealer if you cannot identify the required dimensions or filter type. Lennox’s air-filter instructions direct owners to check the existing filter or consult a dealer.
- Install it in the correct direction. The arrows on the frame indicate airflow and should point toward the furnace or air handler.
For a replacement search, use “HVAC air filter replacement” with the exact dimensions and type printed on your current filter. MERV rating alone does not tell you whether a filter will physically fit or work with your equipment.
How often should you replace a Lennox AC filter?
Lennox gives two different general intervals on its owner-facing pages: its air-filter page says standard disposable one-inch filters should be changed every three months, while its air-conditioner maintenance page says to replace one-inch pleated filters monthly. Those recommendations describe different filter categories and do not establish one interval for every installation.
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#1 Best Overall
- Price For: Each Item: Filter Fits Brand: Lennox Country of Origin (subject to change): Mexico
Check the label on your installed filter and the equipment manual for the interval that applies to your setup. Lennox also notes that continuous use, dusty conditions, and pets can mean more frequent attention. If the filter type or schedule remains unclear, ask a dealer. Do not assume the longer interval applies simply because a replacement filter advertises a long service life.
How Lennox’s Healthy Climate media-filter options compare
The following products are specified for five-inch-box media air cleaners. They are not universal replacements for ordinary one-inch filters, nor proof that every Lennox air conditioner can use them. Confirm that your installed housing is the matching media air cleaner before choosing among them.
Rank #2
- MERV 11
- High-efficiency alternative to one-inch filters
- Fits the X6660 HCC20-28 Air Cleaner
- Nominal Filter Dimensions: 20x25x5 Actual Dimensions: 19-3/4" x 24-3/4" x 4-3/8"
- Genuine Lennox OEM Furnace Filter
| Option | Specified format and rating | Lennox-published particle-removal figures | Listed filter life |
|---|---|---|---|
| Healthy Climate 11 | Five-inch box; MERV 11 | More than 87% down to 3 microns and more than 28% down to 0.3 microns. Lennox attributes these results to lab tests under conditions included in ASHRAE Standard 52.2. | Up to 12 months |
| Healthy Climate 13 | Five-inch box; MERV 13 | Up to 99% down to 3 microns and up to 54% down to 0.3 microns under ASHRAE Standard 52.2 conditions for E1 and E3 size ranges. | Up to 12 months |
| Carbon Clean 16 | Five-inch box; MERV 16 | Up to 99.99% down to 3 microns and up to 95% down to 0.3 microns under ASHRAE Standard 52.2 conditions for E1 and E3 size ranges. | Up to 12 months |
These are manufacturer-published specifications from Lennox Residential; publication dates are not stated, and the pages were accessed in 2026. The figures are laboratory results, not independent comparisons or guarantees of what a filter will remove in a home. Lennox’s Healthy Climate 11 page also notes California Title 24 restrictions on MERV 11 for new equipment installations; verify current local requirements and system applicability before selecting or installing it.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why the highest MERV rating is not automatically best
MERV describes filtration performance, not size or compatibility. A higher rating does not establish that a filter fits your housing or that your system is designed to use it. The cited Lennox specifications do not provide system-specific pressure-drop limits for every Lennox installation, so they cannot support a blanket recommendation to choose MERV 16—or any one rating—for all Lennox air conditioners.
Rank #3
- Nominal Filter Size: 20x20x5 Actual Filter Size: 20" x 19-3/4" x 4-3/8"
Choose only among filters approved for your installed equipment. Use the manual or dealer to confirm the compatible filter type and housing, then compare the exact dimensions and depth. This is especially important when moving from a standard one-inch filter to a five-inch media-air-cleaner cartridge.
Quick Recap
Best Value
- X6675 20x25x5 Air Filter Replacement for your furnace, air conditioner, or HVAC system. The filter and is suitable for hospitals, homes, or just about anywhere.
- Easy Replacement - This 20x25x5 furnace filter has the ability to last up to 1 year! Depending on your home's condition, the filter may be replaced every 6-12 months.
- Use the Wholesalehome cloth to clean your furnace or air handler of all dirt before placing your new furnace filter in.
- Highly Efficient - Being Merv 16, the carbon coated fiber matrix this filter will provide extra deep filtration to help you maintain optimal air quality in your home.
- These 5 inch air filters are compatible with HCC20-28 models as well as many Honeywell, Carrier, and Trion Air Bear models that accept a 20x25x5 filter.
Rank #4
- MERV 16 rating. Actual size: 20-3/4 x 24-3/4 x 4-3/8
- Bundle includes a Same Day Supply reminder magnet (1 per filter) so you know when you last changed your filter without having to open your filter cabinet.
- Filter lasts up to 1 year. As with any filtration product, replacement life cycle depends on the individual conditions and needs of the home.
- Removes over 95% of particles ranging in size down to 0.3 micron and more than 90% of particles 0.01 microns and larger.
- Filters are shipped in individual clear plastic bags that can be reused to dispose of your old filter.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
