Should I Replace My AC’s Evaporator Coil or the Whole AC Unit?

If you’ve been told that your AC’s evaporator coil is damaged, you’re probably thinking—big deal, I can just replace it, right?

Well, it’s not always that easy.

In some situations, replacing just the evaporator coil means it will “mismatch” your condenser (the outside unit). And if the condenser and evaporator mismatch in either age, SEER or refrigerant, you’re going to run into problems like:

• High energy bills
• Frequent repairs
• Less comfort
• A unit that will die much earlier than it should

We’ll explain what we mean by “mismatching” coils and when you should replace the entire unit versus just the evaporator coil. But first, let’s take a quick look at what an evaporator coil does and how it can get damaged.

Your AC’s evaporator coil is responsible for absorbing the heat and moisture in your home.

Translation? Without the evaporator coil, your AC ain’t cooling your home.

Here’s how it works: the evaporator coils are filled with super cold refrigerant. As warm air from inside your home passes over these coils, the refrigerant absorbs the heat and moisture from the air.

From there, the refrigerant travels through lines that eventually lead to the outdoor unit, where the heat it absorbed is dumped into the outdoor air.

Want to learn more about what your evaporator coil does? Just check out our detailed blog, “What Is a Central Air Conditioner Evaporator Coil?”.

The main reason that an evaporator coil would fail and need to be replaced is due to erosion.

Over time, the refrigerant flowing through the evaporator’s coils wears down the inner lining, making the coils weaker. Certain evaporator coil cleaners can also corrode and weaken the outer lining of the coils.

The weaker the coils, the more prone they are to developing refrigerant leaks. And once you have a refrigerant leak, it’s usually more cost-effective to completely replace the coil or entire unit than to repair the leak and recharge the unit with more refrigerant (especially if your AC takes R-22 refrigerant).

While it sounds more cost-effective to just replace the damaged coil, sometimes the alternative—replacing the entire AC—is true.

Why? Well, your AC has two coils:

1. The evaporator coil or the “inside coil”
2. The condenser coil or the “outside coil”

These coils are both housed within the same AC unit but are still separate components that must work closely together to cool your home.

That said, replacing just one of these coils could cause major problems for your unit. Let’s take a closer look at when replacing the entire unit is more cost-effective.

1. Your AC is 8+ years (or older)

Air conditioners last anywhere from 10 to 12 years. That said, if your AC is nearing 8 years old, replacing just the evaporator coil would be like putting a brand new engine into a dying car—it’s just not worth the money.

Plus, if you were to replace the coil, it’d have a near-death partner to work with. Working alongside an old coil that isn’t pulling its weight would put stress on the new coil, causing it to die earlier than it should.

2. The evaporator coil you need to replace is obsolete

Every AC has a “SEER” rating (ranging from 13 to 21) that determines how efficient the unit is. The higher the SEER, the more efficient the unit (and the coil).

The federal minimum SEER rating is 14. But if you have an older unit, it could have a SEER rating that’s a lot lower than that. For example, if you have a 12-SEER unit that needs a replacement evaporator coil, it’s very possible that replacement 12-SEER coils for that model are obsolete and not made anymore. If this is the case, you’ll need to completely replace your unit—otherwise you’d end up with an indoor and outdoor unit with mismatching SEER ratings.

So is it really all that bad if your AC coils are mismatched in SEER ratings? Yes.

Pairing an efficient 14-SEER coil with an older, less efficient coil is like installing a V10 engine in a 10-year-old minivan—you’re just not going to get the performance you’d expect from the engine, right?

Similarly, if you have a low-SEER outdoor coil that’s paired with a highly efficient indoor coil, the outdoor coil will drag down the performance of your indoor coil—which means you’ve wasted the money you just spent on your new evaporator coil.

3. Your AC unit uses R-22

If your unit uses R-22, your best option is to replace the entire unit for one that uses R-410A refrigerant.

You see, R-22 is an older refrigerant that’s harmful to the environment. Because of this, most countries have slowly phased out its use. As of today, no more R-22 refrigerant is being produced, which makes it very expensive.

So, if your evaporator coil has sprung a leak and your unit uses R-22, it could get very expensive to replace the coil and then recharge your unit with more R-22. R-22 is so expensive, in fact, that most HVAC professionals would advise replacing the entire unit—not just the evaporator coil—if you have a refrigerant leak anywhere in the system.