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Evaporator Coil

Evaporator Coils: How They Work, What They Cost, and How to Keep Them Clean

Chances are, you’re not interested in a dysfunctional air conditioner that never turns on. And you’re probably really not interested in an air conditioner that blows out warm air in the middle of a hot summer day. That’s why it’s important you (with the help of a professional HVAC technician) keep your air conditioner’s evaporator coil in the best possible shape.

Your evaporator coil is a major part of your AC unit because it absorbs heat from inside your home. It then works with other parts of your air conditioner to cool your home by transferring all that heat outside.

That means if your evaporator coil is broken, your home won’t get as cool as you want it. Understanding how an evaporator coil works and what you can do to maintain it will play a big role in saving you the heartache of a broken air conditioner in the summer.

So, what is an evaporator coil, exactly?

An evaporator coil is the component of your heat pump or air conditioner that absorbs the heat and moisture from the air inside your house. It works alongside the condenser coil to produce cool air and complete the heat exchange cycle.

Warning: Your air conditioner is a dangerous, high-voltage device. Touching or mishandling the internal components could lead to serious injury or death. Always consult an experienced and licensed HVAC technician if you’re experiencing problems with your air conditioner.

How does it work?

To understand how an AC evaporator coil works, it’s important to understand how an air conditioning unit functions as a whole. Unlike how a furnace produces heat, an air conditioner doesn’t actually produce cold air. Instead, the system removes heat from the air in your home, carries the heat through the air conditioner, and sends that warm air outside. To do this, refrigerant flows throughout the entire air conditioning system, carrying and releasing heat, to ultimately cool the air. This cycle repeats itself continuously until enough heat has been taken out of the air in your home so that the air temperature matches the temperature set on your thermostat.

Evaporator coils are typically made of copper or steel — two metals that conduct heat well. As the refrigerant runs through the evaporator coil, the coil absorbs the heat the refrigerant is carrying. The absorbed heat then moves on from the evaporator coil and throughout the rest of the air conditioner until it’s released outside the home via the condenser coils. As more and more heat is absorbed and released, cool, refreshing air is dispersed throughout your home. Most AC evaporator coils should last between 10 and 15 years, as long as maintenance is regularly performed.

Where is it located?

The evaporator coil is attached to your furnace or inside your air handler, depending on the system. The AC evaporator coil is located inside the portion of the air conditioning unit that sits inside your home and should only be accessed by a trained HVAC professional.

What’s the difference between an evaporator coil and a condenser coil?

Although the evaporator coil and condenser coil work together to cool your home, the two perform very different tasks. While the evaporator coil is responsible for absorbing heat from the refrigerant, the condenser coils are where the refrigerant releases the heat that was taken out of your home.

How do these two work together?

Evaporator coils and condenser coils work in tandem to produce cold air and complete the heat exchange cycle. They form one continuous loop, where the evaporator coils absorb heat and the condenser coils release heat. The cooling process could not be completed without both sets of coils.

More on AC condenser coils

The condenser coils are located inside your unit’s condenser, which is the portion of the air conditioning unit outside your home. The condenser is responsible for turning refrigerant into a hot, highly pressurized gas. This gas then flows through the condenser coils, which are all in the path of blowing air, so the heat from your home is released.

How do you know if your evaporator coil is bad?

There are some telltale signs that let you know when you should hire an HVAC technician to inspect your evaporator coil. You may have a bad AC evaporator coil if your unit is:

  • Not turning on.
  • Releasing warm air from the vents inside your house.
  • Starting and stopping without completing cooling.
  • Making strange noises like a hiss or bang, coming from inside or outside the unit.
  • Producing a refrigerant leak that you can see near the indoor cooling component.

WARNING: AC refrigerant is a toxic chemical. Touching or mishandling AC refrigerant could lead to serious injury or death. Keep small children and pets away from any refrigerant leaks. Always consult an experienced and licensed HVAC technician if you’re experiencing problems with your air conditioner.

If you identify any of these issues with your unit, you may need to contact an HVAC professional to clean or replace your evaporator coil.

Top evaporator coil issues

A licensed HVAC professional can inspect your AC evaporator coils to diagnose the following issues. Do not attempt to inspect or maintain your evaporator coils yourself.

Dust build-up

It’s extremely important to change your air filter on a monthly basis. If you don’t, your evaporator coil may be in jeopardy. When the air filter becomes clogged, excess dust and dirt begin to deposit onto the evaporator coil, causing it to run less efficiently. Dust on an evaporator coil acts as an insulator, keeping the heat in and the air away from the coils. This means your system will have to run longer, use more energy, and potentially face more issues in the future.

Frosting over

Another issue that could arise from a dirty evaporator coil is the entire piece frosting over. If the coil is dirty, the refrigerant running through it won’t be able to warm up as much as it’s supposed to, which causes the water vapor to freeze instead of becoming a liquid. If this keeps happening, the entire coil may freeze and frost over.

Never let your air conditioning unit run with a frosted evaporator coil, because it won’t be able to absorb heat correctly, and could result in the entire AC unit breaking.


Because the evaporator coil is where heat is absorbed, tiny leaks can form from the mixture of condensation and the chemicals found in household air. If you start seeing oily residue on or around your evaporator coil that’s likely a sign it’s leaking and needs to be serviced by a licensed HVAC professional soon.

Why a clean evaporator coil is a good thing

If your AC evaporator coil is dirty, but still functioning, don’t push it off to address later. A dirty, yet still functional, evaporator coil takes a longer time to cool your home and causes lower air quality overall.

Lastly, having your evaporator coil serviced regularly keeps your home at the temperature you desire. A dirty evaporator coil could mean living in a higher temperature environment. Contact a licensed HVAC technician to keep your AC unit in optimal condition.

How to have your evaporator coils maintained and serviced

Your air conditioner is a dangerous, high-voltage device. Touching or mishandling the internal components could lead to serious injury or death. Always consult an experienced and licensed HVAC technician if you’re experiencing problems with your air conditioner.

It’s best to have your evaporator coils cleaned and maintained by a licensed HVAC technician at the same time you’re having your entire AC system cleaned and maintained. Make sure you change your air filters regularly, an HVAC professional inspects and maintains the refrigerant levels in your unit and always report any issues you may see, hear or feel coming from your air conditioning system.

Scheduling regular HVAC maintenance is critical. Always get help from a professional to clean and maintain the inner workings of your unit, including evaporator coils. Very dirty coils may need to be cleaned with heavy-duty chemicals or techniques like power-washing. HVAC professionals are trained and have the proper equipment to safely keep your AC unit and components clean and debris-free.

Preventative tips to avoid bad/dirty evaporator coils

To avoid a bad or dirty evaporator coil, be sure to change your AC unit’s filter monthly, especially in the months when you use your unit more frequently. Also, schedule regular HVAC maintenance with a professional to catch issues early, allow for regular evaporator coil cleaning during regularly scheduled maintenance times, and resolve problems before the entire unit needs replacing.

How low refrigerant can affect evaporator coil performance

Refrigerant is the toxic chemical compound that flows throughout your entire air conditioning unit. When refrigerant is low, your entire unit may fail to function as it should. With regard to AC evaporator coil performance, low refrigerant means there is less chemical coolant flowing through the evaporator coil. That means your AC system won’t be able to absorb as much heat from your home, because less of it is extracted, so it may take longer for your AC unit to reach your desired temperature. When the cooling cycle takes longer to complete, your system will use more energy and experience more wear-and-tear.

Evaporator coil replacement

Your air conditioner is a dangerous, high-voltage device. Touching or mishandling the internal components could lead to serious injury or death. Always consult an experienced and licensed HVAC technician if you’re experiencing problems with your air conditioner.

A licensed HVAC technician will first recover the remaining refrigerant gas in the unit. Next, the technician will solder in a new evaporator coil. Soldering involves melting two metals together to form a permanent connection between your evaporator coil and the other parts in the unit. Once this process is complete, the technician will need to run through the cooling process at least three times, replace the air filter, and adjust any other refrigerant or gas levels the unit needs to run effectively.

Can this be repaired?

If the evaporator coil is leaking or frosted over, it likely can’t be repaired and will need to be replaced. If the evaporator coil is simply dirty, an HVAC professional may be able to use cleaning techniques to repair the coil without replacing it.

How much does it cost to replace an evaporator coil?

Not having to replace your coil can be a good thing for your bank account! Evaporator coil replacement costs can range anywhere from $600 to $2,000, depending on whether your unit’s under warranty or not, according to Costimates. If an HVAC technician is able to repair an evaporator coil without fully replacing it, your wallet is in luck.

If your evaporator coil does need a replacement, your HVAC professional should be able to get the part within a few days. The actual replacement will take a few hours, but once it’s complete your air conditioner should be up and running like before.

Need help?

Contact your local Trane dealer if you suspect your evaporator coil may be dirty or damaged. Remember, never try to clean or replace an evaporator coil yourself; let a professional handle it so you don’t void your warranty.

Contact a local dealer

Dealers can answer questions, help you find the right products for your home, and repair your system.

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