Heat Pump vs Gas Furnace Cost Calculator
Compare yearly heating costs.
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HVAC Repair vs Replace Calculator
Weigh a repair quote against replacing the system. The calculator compares five years of repairs, energy and the value of a new unit’s remaining life, and checks the rules of thumb technicians often quote.
How it works
- Choose the equipment type and enter its age and the repair quote.
- Enter the installed price of a replacement from a contractor quote.
- Add the yearly energy cost of the current unit and how much a new one would save, plus expected repairs and maintenance.
- Read the economic comparison and check the 50% and $5,000 rules alongside it.
Formula
Life left if repaired = max(typical lifespan − age, 2 years) Repair path = repair + (energy + repairs + maintenance) × years kept + new-unit share if it fails within 5 years Replace path = price × 5 ÷ lifespan + (energy × (1 − savings) + maintenance) × 5 50% rule: repair ≥ 50% of replacement and age ≥ half the lifespan · $5,000 rule: age × repair > $5,000
Typical lifespans used: gas furnace 18 years, central AC and heat pump 15, boiler 25. Charging the new unit only for the share of its life used within five years is a standard equivalent-cost approach; the cash rows show what each option actually costs you in that period. Verdicts: repair when it costs at least 15% less, compare carefully within ±15%, otherwise replacement may be economically reasonable.
Example
A 12-year-old air conditioner needs a $2,400 compressor replacement. A new higher-efficiency system is quoted at $7,800 installed and would cut the $900 yearly cooling bill by about 25%.
Inputs
- Equipment
- Central air conditioner
- Age
- 12 years
- Repair quote
- $2,400
- Replacement price, installed
- $7,800
- Yearly energy cost of current unit
- $900
- Energy saved by a new unit
- 25 %
- Other repairs expected per year if kept
- $200
- Yearly maintenance (either option)
- $150
Result
Economic comparisonReplacement may be economically reasonableRepairing costs about 31% more over five years
5-year cost if repaired$8,840
5-year cost if replaced$6,725
Repair as % of replacement31%
Reading the result
A repair that keeps a mid-life system running for years is usually good value. The balance shifts as equipment ages: each repair buys fewer years, older units use more energy, and a failure after an expensive repair means paying twice. The comparison puts those effects into one five-year number.
Rules of thumb are shortcuts to the same question. The $5,000 rule multiplies age by repair cost; the 50% rule compares the repair to the replacement price. They are shown so you can see where your situation falls, but neither accounts for energy savings.
What a calculator cannot judge
Safety and code issues come first. A cracked heat exchanger, a gas leak, or wiring damage is not a cost decision. Older air conditioners that use phased-out R-22 refrigerant can be very expensive to recharge. A qualified HVAC technician should confirm the condition of the equipment; this tool only compares the costs you enter.
Frequently asked questions
What is the $5,000 rule for HVAC?
Multiply the unit’s age by the repair cost. If the result is over $5,000, many technicians suggest replacing; below it, repairing. A 12-year-old unit with a $500 repair scores $6,000.
How long does a furnace or AC last?
Gas furnaces commonly last about 15–20 years, central air conditioners and heat pumps about 12–17, and boilers 20–30, depending on maintenance and climate.
Should I repair a 15-year-old furnace?
A small repair can still make sense, but with little expected life left, larger repairs often favor replacement — especially if a new furnace would noticeably cut gas bills. Enter the numbers to compare.
Does this include rebates and tax credits?
Enter the replacement price after any rebates or credits you qualify for; the calculator does not look them up.