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My Furnace and My Air Conditioner: Should I Replace Them at the Same Time?

For many of us, replacing a furnace and an air conditioner at the same time might sound like a lot of work and especially a lot of money. Plus, it’s more in our nature to replace each unit only if needed close to or during its season of use.

Yet here’s what we should know and consider: Under certain circumstances, replacing both can create a better-matched system that will serve us more efficiently. This in turn can lead to savings that offset or even outperform the initial investment.

Let’s delve into a few leading factors of whether replacing the units together makes good sense.

Age of AC and Furnace

On the average, if they are properly maintained, an air conditioner and a furnace should serve optimally for about 15 years before needing replacement. In some cases, they might continue performing for up to 20 years, but 15 is more the norm.

The advantage of changing them out together is that when you replace the air conditioner, it has to be disconnected from the evaporator coil and other inner components. If you’re replacing the furnace at the same time, everything will already be detached, so financially you’re at an advantage because that work is done. You pay for installation labor once instead of twice, which can mean notable savings.

Compatibility and Seasonal Energy Efficiency Ratio (SEER) Rating

The furnace contains the same blower motor (fan) as the AC for pushing air through your ductwork. If you are installing a high-efficiency air conditioner (typically 16 SEER in our region), and the existing furnace doesn’t have a variable-speed motor, some of the new AC’s performance will be compromised.

The same holds true for replacing a high-efficiency furnace (e.g. 97%). If your air conditioner is 15–20 years old, there’s a good chance it’s not equipped to pair with the new furnace’s efficiency and variable-speed motor. The new furnace will keep you warm in winter, but during summer your cooling may be weakened.


The challenge of replacing a heating and cooling system may influence whether it’s wise to take care of both units at once.

For example, a home might be in a remote area requiring extensive travel time. The furnace might also be in a difficult-to-reach location, such as under the house. Both circumstances can involve additional fees, so arranging for one service visit instead of two can make financial sense.

Discounts and Rebates

Sometimes system manufacturers will offer special offers or rebates when the furnace and the air conditioner are purchased at the same time. During certain promotional periods, an HVAC installation company might also offer a discount when both units are purchased together.

When Not to Replace

There may also be some situations when it’s best not to replace both units at once. If the air conditioner is less than five years old, for example, you can probably hold off on switching it out along with the furnace because you’ll usually have at least another 10 years of good use from it.

Likewise, if the furnace is less than five years old, it will often have at least another 10 years of performance, so you can probably wait until the next time the air conditioner needs to be replaced.

Contact Us Today

As you can see, you have some things to think about when deciding whether to replace the furnace and the air conditioner at the same time. If you still have questions, the Air Dynamics team is always ready to speak with you. We’re here to help you make the best choices for your HVAC in Oswego, Yorkville, Naperville, Aurora or Plainfield. Call us anytime at (630) 731-1550.

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