The short rule for your furnace
You do not need a contractor to make this complicated. Three numbers tell you almost everything about your furnace: how old it is, what the repair costs, and how often it has been breaking down. Run those, and the answer is usually clear. The same three numbers decide an aging AC too, which I cover at the end.
Lean toward repair when
- The system is under about 12 years old and has been reliable.
- The repair is small, like a capacitor, an igniter, a contactor, or a thermostat.
- It is the first real failure, not the third call this year.
- The repair is well under a third of the cost of replacing the system.
Lean toward replace when
Once a system is on borrowed time, every repair is money you will not get back when it fails for good a year later.
- The furnace is 15-plus years old, or the AC is 12-plus, and near the end of its expected life.
- The repair is expensive, like a heat exchanger, a compressor, a control board, or a coil.
- It has needed several repairs in the last couple of seasons.
- The repair cost is more than about a third to half the price of a new system.
- Your bills keep climbing because the system runs inefficiently or short-cycles.
The timing trap to avoid
The worst time to replace a furnace is the moment it dies in a January cold snap, when you are paying emergency rates and taking whatever unit is available. If your system is already old and starting to fail, planning the replacement for the shoulder season, spring or fall, lets you shop the price and avoid the panic. The same goes for an AC on its last legs heading into summer.
What I actually tell people
I am not going to sell you a system you do not need. If your furnace is twelve years old and needs a $200 part, I will tell you to fix it. If it is nineteen and facing a cracked heat exchanger, I will tell you that too, and lay out the replacement and any heat-pump option with the rebates. Either way you get the honest math and a number in writing for free, and a maintenance plan can catch the small stuff before it becomes the expensive stuff.
