Do I Need to Replace Both My AC and Furnace at the Same Time?
Let me guess—you’re dealing with a broken air conditioner or an aging furnace, and your HVAC tech just asked you if you want to replace both units. You’re probably thinking, “Wait… why would I replace something that still works?” As someone who’s been in this industry for over two decades here at U.S. Heating and Air (USHA), I’ve had this conversation with hundreds of homeowners across Delmarva. So, grab a cup of coffee and let me walk you through the real answer—because it depends. Let’s break it down together in a way that makes sense for your home, your wallet, and your comfort.
Why You Might Be Asked to Replace Both AC and
Furnace
First things first—your AC and furnace are part of the same HVAC system. They share components, especially the air handler or blower motor, which is like the heart that pushes air throughout your home.
That’s why when one half of the system gets upgraded and the other doesn’t, you might run into compatibility issues or reduced efficiency. New systems are built to work best with new systems
So, Should You Replace Both at Once? Here’s When It
Makes Sense
1. Both Units Are 10-15+ Years Old
Most air conditioners last 10–15 years. Furnaces? Usually 15–20. If both are nearing retirement,
it might make more financial sense to replace them together rather than staggering it and paying
for installation costs twice.
Plus, today’s HVAC systems are designed to work as a matched system, which gives you the
best energy efficiency and performance.
2. You Want Higher Energy Efficiency
Modern ACs and furnaces are way more efficient than units from 10+ years ago. If you replace
only the AC but keep an old furnace, your system may not qualify for the top SEER ratings or
ENERGY STAR rebates.
That’s like putting a brand-new engine in a rusty old car—it’ll run, but not the way it’s meant to.
3. You’re Planning to Stay in Your Home Long-Term
If this is your forever home, investing in a full system upgrade pays off in lower energy bills,
fewer breakdowns, and better comfort year-round. You’ll also be covered under a single
warranty, which makes service simpler.
4. The Furnace Is Showing Signs of Age or Repair Needs
Even if the AC is the one that failed, pay attention to your furnace. Does it rattle? Need frequent
repairs? Have rising energy bills? If so, combining the replacement might save you more in the long run than doing it piecemeal.
5. You’re Upgrading to a New Refrigerant (like R-454B)
Big industry changes are happening with refrigerants—goodbye R-410A, hello R-454B. If you upgrade your AC to a system that uses R-454B but keep your old furnace, you may face compatibility issues down the road. At USHA, we always recommend a future-proof setup.
When It’s Okay to Replace Just One
customer. So here’s the truth:
● If your furnace is less than 10 years old and running efficiently, and your AC needs
replacement due to a breakdown or R-410A phase-out, you can just replace the AC.
● Likewise, if your AC is newer and your furnace bites the dust, you can just replace the
furnace.
But remember, the new unit might need to be customized or adjusted to work well with the older
one, and efficiency could take a small hit.
The Real-World Example (From My Toolbox)
years old. We checked compatibility, efficiency ratings, and determined that upgrading only the
AC made sense for now. I saved him over $3,000 in unnecessary costs.
Three years later, we replaced the furnace—and the customer had planned and budgeted for it
stress-free. That’s how we do things at USHA: honest advice, real results.
Final Verdict: One or Both?
Here’s a quick cheat sheet:
Both units are over 12–15 years ❌ ✅
You want max energy efficiency ❌ ✅
You’re upgrading refrigerants ❌ ✅
Short-term home plans ✅ ❌
Staying long-term or want a warranty match ❌ ✅
Let’s Talk About Your Home
answer. If you’re facing the “replace one or both” question, don’t go it alone.
Give us a call at U.S. Heating and Air, and we’ll give you an honest evaluation—no pressure,
just what’s best for you.
FAQs: Replacing AC and Furnace Together
Can I replace my AC without replacing the furnace?
Yes, you can—but it depends on the age and efficiency of your furnace. If your furnace is under 10 years old and in good condition, replacing just the AC might be fine. Just keep in mind you might miss out on maximum efficiency and warranty benefits of a matched system.
Will a mismatched HVAC system affect my energy bills?
It can. When an old furnace is paired with a new, high-efficiency AC (or vice versa), the components may not work together optimally. That mismatch could lower system performance and increase your energy costs over time.
Is it cheaper to replace both units at once?
In many cases, yes. Replacing both systems in one visit can save on installation labor, reduce repeat service calls, and allow you to take advantage of bundled rebates or special financing. You’ll also avoid paying for another install down the road.
How do I know if my furnace is compatible with a new AC unit?
Compatibility depends on things like the blower motor, coil size, and refrigerant type. At USHA, we inspect your current system and verify whether your existing furnace can support a new AC. We never guess—we test.
What’s the best time of year to replace my AC and furnace?
Spring and fall are usually the sweet spots. Demand is lower, prices are often better, and you won’t be stuck in the middle of a heatwave or a cold snap during installation.