Top rated by 7291 customers

Geothermal air filters

Buy replacement air filters for geothermal heat pump systems. Choose from 1000+ available sizes or order custom geothermal filters with free shipping over $50.

Geothermal air filters

Filter size finder

Find the geothermal filter you need by entering the width, length and depth or choose your size in the table below.

Filter Finder
Can't find your size? Create your own custom geothermal filter
Easy Installation

Easy Installation

Fits right into your system, no tools needed

Durable & long-lasting

Durable & long-lasting

Premium quality pleated filters in a rigid frame

All sizes available

All sizes available

Find your perfect fit with our complete size range

Guaranteed to fit

Guaranteed to fit

Compatible with all the major HVAC unit brands

Find your geothermal filter size

Shop by Size

10,000+ satisfied customers

google
  • *
  • *
  • *
  • *
  • *

4.6 stars, 4478 reviews

amazon
  • *
  • *
  • *
  • *
  • *

4.6 stars, 3597 reviews

  • *
  • *
  • *
  • *
  • *

"Quality filters at great prices"

  • *
  • *
  • *
  • *
  • *

"Easy to order and shipped fast"

  • *
  • *
  • *
  • *
  • *

"Thankful for this product being available!"

  • *
  • *
  • *
  • *
  • *

"no comments."

  • *
  • *
  • *
  • *
  • *

"Great selection and price."

  • *
  • *
  • *
  • *
  • *

"Fits great"

  • *
  • *
  • *
  • *
  • *

"Filters are just what I needed and in the right size. They shipped in a timely fashion."

  • *
  • *
  • *
  • *
  • *

"Amazing"

  • *
  • *
  • *
  • *
  • *

"affordable and just what I needed! Will be buying more when needed! Shipping was quick also!"

  • *
  • *
  • *
  • *
  • *

"Very fine!"

Read more reviews

When to replace your geothermal filter?

For best indoor air quality, we recommend you change your filters regularly at different times depending on your situation.

<
  • Asthma

    Asthma or allergies

    Every 6 weeks

    Replace your air filter every 6 weeks to minimize the circulation of bacteria and allergens in the air.

  • Pets

    Pets

    Every 2 months

    Replace air filters every 2 months to reduce odors as well as pet dander and hair buildup in your system.

  • Children

    Young children

    Every 2-3 months

    Replace your air filter every 2-3 months to reduce airborne particles and maintain cleaner indoor air.

>

Stay On Schedule And Save 5%

Keeping your geothermal filter replacement schedule in mind can be challenging to say the least. Make your life easier with Filter King’s auto delivery subscription.

  • Get 5% off your order
  • Choose your delivery frequency
  • Change or cancel any time
Filter King&#039;s auto delivery service

MERV rating comparison

 
Recommended for
Comparable ratings
Filtration efficiency
Dust mites
10+ microns
Pollen
10-100 microns
Pet dander
5-10 microns
Lint and fabric fibers
10+ microns
Mold spores
3-10 microns
Fine dust
1-3 microns
Smoke particles
0.3-1 micron
Smog and fine particles
0.1-1 micron
Bacteria
0.3-5 microns
Virus carriers
0.3-1 micron
Odors and gases
Molecular level
VOCs
Molecular level
Cooking odors
Molecular level
Learn more
MERV 8
Basic air quality,
standard homes
FPR 5,
MPR 600
90% of common particles
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
No
linkMERV 8 filters
MERV 11
Better air quality, homes with allergies, pets
FPR 7,
MPR 1000-1200
95% of common particles
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
linkMERV 11 filters
MERV 13
Superior air quality, health concerns, allergies
FPR 10,
MPR 1500-1900
98% of common particles
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
linkMERV 13 filters
MERV 8 Carbon
Odor control, cooking smells, pet areas
FPR 5 + Carbon,
MPR 600 + Odor
90% of common particles
Yes
Yes
Yes
Yes
Yes
No
Yes
No
No
No
Yes
Yes
Yes
linkOdor eliminator filters

How to find your geothermal filter size?

Check the label on your current filter or use a tape measure to determine the length, width, and thickness. Just make sure you know the difference between nominal and actual size.

nominal vs actual air filter size

Nominal Size Nominal size

Nominal size is what you normally see printed on the label. This is usually a rounded size which is often not the true size of your filter.

Actual Size Actual size

Actual size is the true size of the air filter, usually written in smaller font below the nominal size.

Measuring

Measure your current air filter or the length, width, and depth of the opening slot to get the actual size. Round it up to the nearest whole inch to get the nominal size.

Why Choose Geothermal Filters

Why homeowners choose Filter King geothermal filters

Made in the USA

All our filters are made in the USA using quality materials — UL Classified and MERV rated to ASHRAE standards for reliable performance you can count on.

Easy to return/
exchange

Try it risk-free. Ordered the wrong size? Not what you expected? Send it back within 30 days for an exchange or a full refund. Simple as that.

Fast & free shipping

Free shipping on orders over $50, and most orders are processed within 24 hours. No waiting around — we get your filters out the door fast.

Frequently asked questions

Frequently Asked Questions (FAQs)

Are geothermal filters different from regular air filters?

No. Geothermal heat pumps use standard air filters — the same ones used in furnaces and HVAC systems. Just match the size and MERV rating your system requires. There's no need to buy a filter specifically labeled geothermal.

How often should I change my geothermal filter?

It depends on the filter thickness. 1-inch filters should be replaced every 30 to 60 days. 2-inch filters can last 60 to 90 days. 4-inch and 5-inch filters can go 6 to 12 months between changes.

Replace your filter more often if you have pets, allergies, or live in a dusty area. A good rule: check it monthly and replace it when it looks gray or clogged.

Which way does the arrow go on a geothermal filter?

The arrow points toward the geothermal, in the direction of airflow. Air flows from your home into the return duct, through the filter, and into the geothermal — so the arrow should face the geothermal or blower motor.

Look for the arrow printed on the filter frame. If you install it backwards, the filter won't work properly and can restrict airflow.

What does a dirty geothermal filter look like?

A clean filter is white or off-white and you can see light through it. A dirty filter looks gray or brown, and the surface will be visibly clogged with dust, lint, and debris.

If you're not sure, hold it up to a light. If little or no light passes through, it's time to replace it.

Where is the geothermal filter located?

Most geothermal filters are located in one of three places: inside the blower compartment of the geothermal, in a slot between the return duct and the geothermal, or behind a return air vent on a wall or ceiling.

Check near your geothermal first — look for a removable cover or a slot where the filter slides in. If you have a return vent with a large grille, the filter may be inside there instead.

What size geothermal filter do I need?

Check your current filter — the size is printed on the frame. You'll see three numbers: length, width, and depth (for example, 16x25x1).

If there's no label, measure the filter yourself. Measure length and width first, then depth (thickness). Round to the nearest inch. If your size is unusual, you may need a custom-sized filter.

Can geothermal filters be recycled?

Most disposable geothermal filters cannot be recycled through regular curbside programs. They contain a mix of cardboard, fiberglass or synthetic fibers, and trapped dust and debris, which makes them difficult to process.

Check with your local waste facility for specific guidelines. Some areas accept them as bulky waste. The cardboard frame can sometimes be separated and recycled on its own if it's not contaminated.