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Comparison · Free

Repair or Replace Calculator

Compare the economics of repairing a failing system against replacing it outright.

The system

A cracked heat exchanger ends the conversation — that is a carbon monoxide hazard, not a repair decision.

years

Typical service life is 15–20 years, with 18 as the planning figure.

The two prices
$

The repair in front of you, parts and labor.

$

National range is $3,500–$6,500. Replace this with your own quote when you have one.

$/yr

Set this to zero for anything that does not consume energy, or if you are replacing like for like.

The decision

Replace it

The repair is 18.0% of replacement cost on a system with 2.0 years of expected life left.
Repair, per year$900 spread over the 3.0 years it buys
$300/yr
Replace, per year$278/yr over 18 years, less $180 of energy saving
$98/yr
The 50% rule saysThe repair is 18.0% of replacement cost
Repair
Life consumed16 years against a 18-year expected life
88.9%
Total cost of each path, including the energy difference
HorizonRepair nowReplace nowDifference
Next 5 years$6,440$5,000$1,440 more to repair
Next 10 years$6,440$5,000$1,440 more to repair
Next 15 years$6,440$5,000$1,440 more to repair

The 50% rule and the cost-per-year test disagree here

The 50% rule looks only at the two prices. It cannot see that this system is 16 years old and that the repair realistically buys 3.0 more years. Cost per remaining year is the better test, because it is the only one that prices what you are actually getting for the money.

What this assumes

  • Applies a cost-per-remaining-year comparison rather than a single rule of thumb.
  • Typical service lives are drawn from manufacturer and industry association averages.
  • Efficiency savings assume the national average energy price unless you enter your own.

Understanding the result

The 50% rule, and its limits

The common guidance is to replace when a repair costs more than half of replacement. It is a reasonable starting point but ignores remaining life. A $700 repair on a 4-year-old furnace and the same repair on a 19-year-old furnace are completely different decisions.

Cost per remaining year is the better test

Divide the repair cost by the years it realistically buys you, and compare that with replacement cost divided by the new unit's expected life. If the repair costs more per year than the replacement does, replace. This handles the age question that percentage rules ignore.

Count the second repair

A system failing in one place at end of life rarely stops there. When a unit is within a few years of its expected life, price the repair as the first of two or three, because that is usually what happens.

Common questions

At what age should I replace my furnace?
Most furnaces run 15 to 20 years. Past 15, a major repair such as a heat exchanger or control board usually favors replacement, particularly if efficiency gains and available rebates are factored in.

You may also need

The next decision usually follows directly from this one.

Related trades

Where to go next