Do You Really Have to Replace the AC and Furnace at the Same Time?
(Short answer: No. But here’s when it might make sense.)
A question that comes up when its time to replace either the AC or furnace is: “Do I have to replace both the AC and furnace at the same time?” And the answer is simple: no, you don’t. If one half of your system is still running strong, there’s no rule (or law of physics) that says you’ve got to toss it out just because the other side tapped out.
But—and there’s always a “but”—there are a few good reasons why people choose to replace both at the same time. So let’s break it down.
You Don’t Have To
If your furnace is newer, still under warranty, or just hasn’t given you any trouble, there’s absolutely no harm in keeping it. Same goes for the AC. These systems are independent in a lot of ways—different components, different jobs—so replacing one doesn’t automatically mean the other is on borrowed time.
In fact, I’ve replaced a lot of AC units where the furnace kept chugging along for another 5, 10, even 15 years. If it’s working, safe, and efficient enough for your needs, leave it alone.
But Here’s When It Makes Sense to Do Both
1. Cost Efficiency (Believe it or not)
Combining the install means one service visit, one crew, one setup. That usually means less total labor cost. Plus, many manufacturers bundle furnace/AC combos with better rebates or extended warranties when installed as a matched system. So while the upfront cost is higher, the dollars-per-component can actually be lower.
2. Performance and Compatibility
Today’s high-efficiency AC systems (especially variable speed or inverter units) are designed to talk to matching furnaces for things like airflow control, humidity management, and communication-based diagnostics. If your furnace is old-school single-stage, it may work with your fancy new AC—but it won’t let it perform at its best.
Think of it like upgrading half a stereo. Sure, the new speaker sounds great, but you’re still bottlenecked by the old amp.
3. Age and Reliability
If both systems are close in age—say, 15-20 years old—it’s not crazy to assume the second one’s not far behind. If your AC dies in July, and then your furnace gives up the ghost in January, that’s two emergency calls in less than a year. Replacing both at once means fewer surprises and fewer disruptions.
4. Financing and Planning Ahead
If you’re financing the install, lumping both into one loan means one payment, one term, and fewer credit pulls. It’s also easier on your future self to plan and budget for one big upgrade rather than two scattered ones.
Bottom Line
You don’t have to replace both the AC and furnace at the same time. But in certain situations—aging equipment, performance upgrades, financial incentives—it can be the smarter long-term play.
My advice? Have a tech you trust take a look at both systems. Get the facts, not just the sales pitch. If your furnace’s got years left, keep it. If it’s on borrowed time, it might be cheaper and simpler to rip the Band-Aid off now.
Either way, it’s your house, your comfort, and your wallet.
Premier Mechanical – www.claimyourcomfort.com – 720.207.6812