Can I Replace Just the Outside AC Unit in My Home? (2024)

When summer rolls around, you blast your AC to keep cool from the sweltering heat. However, this year is different. Your outdoor AC unit is well over its intended lifespan, and things aren’t as cool as they used to be. Now, you’re left with a dilemma: Should you replace just the outdoor unit or both AC units? We’ll help you make the call.

Can You Replace Just the Outside Air Conditioning Unit?

If your unit is less than five years old, it might still be under warranty. In that case, you can probably replace just the outside air conditioning unit. Unfortunately, in most other cases, you’re probably better off replacing both the indoor and outdoor units. Here’s why.

Your Old Refrigerant Will Not Be Compatible With Your New AC Unit

If you have an air conditioner that’s over 10 years old, it will be next to impossible to find an outdoor unit that is compatible with your indoor unit. Older ACs use Freon. What is Freon? It’s a refrigerant, technically called R-22, that hasn’t been manufactured in the United States since 2010. According to the Environmental Protection Agency, manufacturers halted production after learning it’s harmful to the ozone layer.

Newer air conditioners use R-410A, R-407C, and R-134a to enhance cooling and energy efficiency. Unfortunately, you can’t mix and match your AC units as you do with socks. If you have an older indoor unit using R-22, it won’t be compatible with an outdoor AC that uses R-410A.

Mismatched Indoor and Outdoor AC Units Can Lead to More Problems

HVAC compatibility doesn’t stop at refrigerant. There are other factors at play—like your AC coils and valves, the SEER rating, and the manufacturer.

“We once only changed out the outer part of a split system, but that was because the inside component was impossible to access, as the homeowner had done remodeling that occluded the inside unit,” says Bob Tschudi, Expert Review Board Member and general contractor in Raleigh, NC. “We were able to get the inside unit motor replaced but not the housing and electronics. The homeowner understood that the impending replacement of the inside unit would involve wall removal and changes to the remodeled space.”

In other words, if the compatibility isn’t up to snuff, it makes room for a whole host of problems. Here are some of the most common issues.

Decreased Efficiency

Central AC has two sets of coils—evaporator coils (in the indoor unit) and condenser coils (in the outdoor unit). If these coils aren’t compatible, efficiency will suffer. In addition, your AC valve—which controls refrigerant flow for your coils—will need to work harder.

As a result, replacing the outdoor unit alone can cause reduced energy efficiency (meaning you’ll see higher electric bills), uncomfortable temperatures, and wear and tear on your system.

Lower SEER Rating

SEER or Seasonal Energy Efficiency Ratio measures how efficiently your air conditioner cools. The higher the rating, the more efficient your unit is.

However, replacing the outdoor AC alone will cause your unit’s SEER rating to drop, resulting in an inefficient system and all that comes with it.

Voided Warranties

During initial AC installation, there’s usually a warranty that covers defects or breakdowns. It only applies to the unit manufacturer.

If you replace only one part of your AC, it will void your warranty since the manufacturer isn’t the same.

Premature Cooling Failures

As you know, regular HVAC maintenance can help your system last between 10 and 15 years. If you only replace the outdoor unit, system incompatibility can significantly shorten that lifespan because it will have to work twice as hard to meet your cooling needs.

You’ll also have frequent HVAC repairs on your hand, which could add up over time. Avoid this process by replacing the indoor and outdoor ACs at the same time.

Benefits of Replacing Both Indoor and Outdoor AC Units

A new AC unit costs $3,800 to $7,500. You might be tempted to save a buck on a partial replacement, but replacing both units is often well worth the full price. Here are some of the ultra-cool benefits.

Save on Cooling Costs

A stressed system bleeds energy. If you want to improve your HVAC system’s efficiency, both the indoor and outdoor AC units should be fully compatible (i.e. you’ll probably need to replace them both). The good news is that higher efficiency means lower energy bills—and the environment will thank you, too.

Increase Comfort in Your Home

A stressed air conditioner will struggle to meet your household needs. It may not reach the temperature on the thermostat or you might notice uneven cooling throughout your home. Replacing both the indoor and outdoor units ensures that your system runs properly, which makes your space more comfortable. Say goodbye to the feeling of dread as a heat wave creeps up the 10-day forecast.

Active HVAC Warranty

If you replace both components, you’ll likely have an active warranty instead of a voided one. Why is this so important? A warranty protects your investment. If there’s a premature problem, you won’t have to shell out thousands to replace or repair your AC.

When Is Replacing One Part of the System a Good Idea?

It’s generally beneficial to replace both the indoor and outdoor AC units—but there is one exception. If your air conditioner is only three to five years old, it might still have warranty coverage.

In that case, check with your manufacturer to see if they’ll cover the replacement of the outdoor unit. If so, they’ll send you an outdoor unit that’s compatible with the rest of your system since the indoor unit is relatively new.

Anything older will result in the need to replace both units. However, you should hire an AC repair company near you and consult with them to figure out the best solution.

Conroy Baltimore contributed to this piece.