Clean your heat pump coils twice a year to keep the system running efficiently

Heat pump coils collect dust, pollen, and debris that block airflow and force your system to work harder. Cleaning them takes about an hour and requires only a soft brush, a garden hose, and a fin comb—no special tools or chemicals. You can do this yourself on the outdoor unit without calling a technician, though the indoor coil is trickier and sometimes worth leaving to a professional.

The best time to clean is spring (before cooling season) and fall (before heating season). If you live somewhere dusty or have pets, you may need to clean every three months instead. A clogged coil doesn't just waste energy—it can cause your heat pump to freeze up in winter or overheat in summer, leading to expensive repairs.

Key Takeaways

  • Turn off power to the heat pump at the breaker before you start, and wait at least five minutes for the system to discharge.
  • The outdoor coil is the easier one to clean yourself using a soft brush and low-pressure water from a garden hose.
  • Never use a pressure washer or stiff brush on the coils, as you can bend the aluminum fins and reduce airflow even more.
  • A fin comb (a cheap tool sold at hardware stores) can straighten bent fins, but only if the damage is minor.
  • If water won't drain from the indoor coil or the system freezes after cleaning, the indoor coil may need professional attention.

Turn off power and let the system discharge

Before you touch anything, switch off the heat pump at the breaker panel in your home. This is not optional—the outdoor unit holds an electrical charge even when the system is off, and touching a live component can cause serious injury.

After you flip the breaker, wait at least five minutes. This gives the capacitor time to fully discharge. If your system has a disconnect switch mounted on or near the outdoor unit itself, flip that too. Some units have both a breaker and a disconnect; use both.

Inspect the outdoor coil for visible dirt and damage

Walk around the outdoor unit and look at the coil fins—the thin metal sheets stacked together on the sides of the unit. If you see thick dust, leaves, or pet hair matted against them, that is what you are cleaning. Light dust is normal and does not always need cleaning.

While you are looking, check whether any fins are bent or crushed. Bent fins reduce airflow just as much as dirt does. If you see only a few bent fins, you can straighten them later with a fin comb. If the whole coil looks mangled, stop and call a technician—you cannot fix that yourself.

Brush away loose debris by hand

Use a soft-bristled brush (like a soft paintbrush or an old toothbrush) to gently brush away loose dust and debris from the coil fins. Brush in the direction the fins run—usually up and down on the sides of the unit. Do not scrub hard or use a stiff brush; you are trying to loosen dust, not remove the coating on the fins.

Pay special attention to the corners and edges where debris collects. Brush the top of the unit too, since leaves and dirt settle there. This step alone removes most of the buildup and takes only a few minutes.

Rinse the coil with low-pressure water from a garden hose

Attach a standard garden hose to an outdoor faucet and set it to a gentle spray—the kind you would use to water plants, not to wash a car. Stand to the side of the unit and spray the coil fins from the inside out, pushing water through the coil rather than against it. Spray gently and let the water do the work.

Do not use a pressure washer under any circumstances. Even on the lowest setting, a pressure washer can bend the fins, crack the coil, or force water into electrical components. A garden hose at normal pressure is all you need. Rinse for two to three minutes, then let the water drain and the coil air-dry for at least 30 minutes before you turn the system back on.

Straighten bent fins with a fin comb if needed

If you spotted a few bent fins during your inspection, you can straighten them using a fin comb—a small, inexpensive tool that looks like a comb with teeth spaced to match your coil's fin spacing. You can buy one at any hardware store for five to fifteen dollars. The comb comes in different sizes; check your coil's fin spacing (usually printed on the unit label) and buy the matching size.

Gently slide the comb through the bent fins, moving slowly and letting the teeth straighten them as you go. Do not force it or work too fast. If a fin is severely bent or kinked, stop—forcing it can crack the coil. A fin comb works only on minor bends. If more than a few fins are damaged, the coil needs professional repair.

Know when to call a technician for the indoor coil

The indoor coil sits inside your furnace or air handler, usually in a closet or basement. It is harder to reach and easier to damage, so most homeowners should not attempt to clean it themselves. If you notice water pooling under your indoor unit, or if your system freezes up even after you cleaned the outdoor coil, the indoor coil may be clogged or dirty.

A technician has the tools to safely access the indoor coil, clean it without damaging it, and check the condensate drain line (which often clogs at the same time). This usually costs between 150 and 300 dollars, but it prevents much more expensive repairs down the road. If you are comfortable working inside your furnace and have the right tools, you can attempt it—but if you are unsure, call a professional.

Turn the system back on and monitor for problems

Once the coil is dry (at least 30 minutes after rinsing), flip the breaker back on. If your unit has a disconnect switch, flip that too. The system should start normally. Listen for unusual noises and feel the air coming from your vents—it should feel warmer in heating mode or cooler in cooling mode than it did before you cleaned.

If the system does not start, or if it starts but then shuts off after a few minutes, turn it off again and wait an hour. Sometimes moisture inside the unit needs time to evaporate. If the problem persists, or if you hear a hissing sound or smell burning, turn off the system and call a technician—you may have accidentally damaged something.

Frequently Asked Questions

How often should I clean the outdoor coil?

Clean it at least twice a year—once in spring and once in fall. If you live in a dusty area, near trees that shed leaves, or have pets that shed heavily, clean it every three months. A clogged coil makes your system work harder and costs more to run.

Can I use a pressure washer on the coil?

No. A pressure washer can bend the aluminum fins, crack the coil, or force water into electrical parts. Use only a garden hose on a gentle spray setting. The low pressure is enough to rinse away dirt without causing damage.

What if water is pooling under the indoor unit?

This usually means the condensate drain line is clogged, not the coil itself. Call a technician to clear the drain. Do not try to fix it yourself unless you are experienced with HVAC systems—you can accidentally damage the drain or push the clog deeper.

Do I need chemicals to clean the coils?

No. Water and a soft brush are enough for routine cleaning. Commercial coil cleaners exist, but they are not necessary for most homeowners and can damage the coil if used wrong. Stick with water unless a technician tells you otherwise.

What if the system freezes after I clean it?

Turn off the system and let it thaw for several hours. Freezing after cleaning usually means the indoor coil is clogged or the refrigerant charge is low. Call a technician—this is not something you can fix yourself, and running a frozen system can damage the compressor.