Evaporator coil replacement cost

Replacing an evaporator coil costs $900 to $2,800, or $600 to $1,300 if the part is still under the manufacturer's warranty and you are only paying labor and refrigerant. It is the indoor half of the cooling system, it sits on top of the furnace or inside the air handler, and it is the second most expensive component after the compressor.

It also fails more often than it should. Coils built between roughly 2005 and 2015 are known for formicary corrosion, a microscopic pinhole leak that develops from the inside out.

What it costs

Attic and crawl space installations sit at the top of the range, because getting a coil in and out of an attic is most of the labor.

How you know it is the coil

The symptom is a slow refrigerant leak: the system cools less each season, ices up on the indoor lines, and eventually stops cooling at all. A technician finds the charge low, traces the leak, and it is at the coil.

Ask how the leak was located. Nitrogen pressure testing or electronic detection is a diagnosis. "The charge was low so it must be the coil" is a guess, and the leak is sometimes at a $15 service valve core instead.

Check the warranty first

Most manufacturers warrant the evaporator coil for five to ten years, and ten to twelve to the original owner where the system was registered after installation. Given the corrosion problem, a fair number of coils fail inside that window.

Take the model and serial numbers off the coil's data plate or the air handler and look them up on the manufacturer's site yourself. Labor is not covered, but the part is most of the bill.

Match the coil to the outdoor unit

A coil is not a generic part. It is rated as a matched pair with the condenser, and the pairing is what the efficiency rating and the compressor warranty are based on.

A mismatched coil costs efficiency, can shorten compressor life, and often voids the outdoor unit's warranty. If your outdoor unit is R-410A, the coil must be an R-410A coil with the right metering device. If your outdoor unit is R-22, you are being told something about the age of the system.

The question this always raises

A $2,400 coil on a system that is nine years old is a genuinely hard call. The arithmetic:

An $11,000 changeout over fifteen years is about $733 a year. A $2,400 coil that buys six more years is $400 a year, which is better. A $2,400 coil that buys three more years is $800 a year, which is worse.

So the answer turns on how much life is left in the compressor and the outdoor coil, not on the price of the part.

Replace the coil when the system is under about ten years, the outdoor unit is sound, and the refrigerant is R-410A or newer.

Replace the system when the compressor has also been repaired, the refrigerant is R-22, the system is past twelve years, or the coil is the second significant failure in two seasons.

Frequently asked questions

Can a leaking coil be repaired instead of replaced?

Sometimes a single accessible leak can be brazed. Formicary corrosion cannot be: it is thousands of microscopic pinholes across the whole coil, and sealing one just moves the problem. Sealant products injected into the refrigerant loop are a bad idea and most manufacturers void the warranty over them.

Why did a nine year old coil fail?

Most likely formicary corrosion, caused by trace volatile organic compounds in indoor air attacking the copper. It is not something you did. Newer coils use different alloys and coatings and fail less.

Does replacing the coil improve efficiency?

Only back to what the system was. A new coil on an old condenser does not lift the SEER rating; it restores the cooling you lost as the charge leaked away.

How long does the job take?

Four to eight hours. The refrigerant is recovered, the plenum opened, the old coil removed, the new one fitted with a new filter drier, then a nitrogen pressure test, a vacuum and a weighed recharge. If nobody pulls a vacuum, moisture stays in the loop and the compressor pays for it later.

Should I replace the furnace at the same time?

If the furnace is over about twelve years old, seriously consider it. The coil sits directly on the furnace, so replacing the furnace afterwards means opening the refrigerant system again and paying much of this labor twice.