Should I Replace My AC's Evaporator Coil or the Whole AC System?

If a technician tells you that your AC’s evaporator coil is damaged, you might think that it’s no big deal if it can be easily replaced, right?

Well, it’s not always that easy. In many scenarios, replacing the evaporator coil means that it no longer matches the condenser (the outdoor unit) in age, SEER rating (an air conditioner’s efficiency grade), or refrigerant type. A mismatch between the condenser and evaporator coil can cause problems like higher energy bills, frequent repairs, less comfort in your home, and a system with a shorter lifespan.

In this blog, we’ll cover:

We’ll explain what we mean by “mismatching” coils and when you should replace the entire system 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 air conditioner both cools and dehumidifies your home. The evaporator coil plays a vital part by absorbing heat and moisture from the warm indoor air. Basically, without a functional evaporator coil, the AC cannot properly cool your home.

How does the evaporator coil function? It’s an A-shaped web of copper tubes located in the heart of your AC system. During a normal cooling cycle, the blower fan pulls warm air from inside your home and blows it over these small copper tubes.

The copper tubes house a super cold chemical refrigerant that absorbs heat from the warm air passing over the coils. This refrigerant cycles between liquid and gas phases. Once it has absorbed enough heat from your home to reach your desired set temperature on the thermostat, it then travels through lines connecting your indoor and outdoor AC units to dump that heat and moisture outdoors. The blower fan then pushes cold air back into your home.

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

The main reason an evaporator coil would need replacement is erosion from normal wear-and-tear. Over time, the refrigerant flowing through it will wear down the inner lining, weakening the coil and causing it to fail. Also, certain evaporator coil cleaners can corrode and weaken the coils’ outer lining. Older forms of refrigerant, such as R-22, are also more toxic and add to the coil corrosion.

A weak evaporator coil is more prone to developing refrigerant leaks. Once a refrigerant leak occurs, it’s typically more cost effective to completely replace the coil or entire system than to repair the leak and recharge the unit with more refrigerant.

Why is that the case? Well, technically, your air conditioner has two coils. Beyond the evaporator coil, it has a condenser coil as part of your outdoor AC unit. Both of these coil parts need to work closely together in order to cool your home. If they are mismatched on certain criteria (which we’ll cover next), they don’t work as well together as they could, increasing your energy bills and potentially causing breakdowns.

Plus, an evaporator coil replacement is costly by itself. A new evaporator coil can cost anywhere from $300 to $1,200 and takes 3+ hours to complete, potentially leading to higher labor costs than other AC repairs. In contrast, a total system replacement ensures a match between the coils, leading to increased AC efficiency.

Let’s take a closer look at when replacing the entire unit is more cost effective.

Learn more about refrigerant leaks in our blog, "4 Signs Your AC May Need a Refrigerant (Freon) Charge."

Depending on the specifications of your AC system, it can be better for your wallet and AC performance to replace the entire thing instead of replacing just the evaporator coil.

If your AC falls under these circumstances, you should consider replacing the whole system. Contact a professional HVAC technician to help you evaluate the cost benefits and your replacement options.

Air conditioners usually last anywhere from 8 to 10 years in Arizona. That said, when it starts nearing its 8th birthday, replacing just the broken evaporator coil can be a lot like putting a brand new engine into a dying car. It’s not worth the money.

Plus, replacing the evaporator coil means you’ll have a new one working alongside a near-death condenser coil. The new part will have to strain to compensate for the older outdoor unit, requiring additional energy.

Every air conditioner has a SEER rating (Seasonal Energy Efficiency Ratio) that indicates the system's efficiency at heat transfer. This rating ranges from 14 to 20+ and the higher the rating, the more efficient the system—and evaporator coil—will be.

Currently, the federally mandated minimum SEER rating by the Department of Energy is 14. However, older systems generally have lower SEER ratings than the requirement. For example, you might have a 12-SEER system that needs a replacement evaporator coil, but that model is no longer made. In this case, you’ll need to completely replace the system or else risk replacing the evaporator coil with a higher SEER rating than the outdoor unit.

So, is it really all that bad for your evaporator coil and condenser coil to have mismatching SEER ratings? Yes. For a car analogy, pairing a new evaporator coil with an older condenser coil is like installing a V10 engine into a decade-old minivan. You will not get the performance you’re looking for and have wasted your money.

As we mentioned above, the evaporator coil houses refrigerant. Depending on the generation of refrigerant, you may need to replace the entire system.

An older form of refrigerant called R-22 harms the ozone layer. Governments across the globe started phasing it out of manufacturing for environmental reasons. As of today, no manufacturer still produces it, making the scarce remaining supplies prohibitively expensive for contractors. If there is a refrigerant leak in the evaporator coil, you might be looking at a hefty price to recharge it.

If your unit uses R-22, your best option is to replace the entire unit with one that uses a new generation of environmentally-friendly and affordable refrigerant called R-410A.