Gas furnaces last 15–25 years. Central air conditioners last 10–20 years. Heat pumps run year-round and typically reach 10–20 years, though the higher annual run hours mean the lower end of that range is more common. Here’s the full table and the formula for deciding when age changes the math on a repair.
Lifespan by equipment type
| Equipment | Typical range | Average well-maintained |
|---|---|---|
| Gas furnace | 15–25 years | 18–20 years |
| Central air conditioner | 10–20 years | 15 years |
| Air-source heat pump | 10–20 years | 15 years |
| Mini-split (inverter heat pump) | 15–20 years | 18 years |
| Sheet metal ductwork | 20–30 years | — |
| Flex ductwork | 10–20 years | — |
AHRI uses a 20-year modeling life for gas furnaces and a 15-year modeling life for central AC and heat pumps in efficiency standard calculations. These are statistical averages, not guarantees: well-maintained equipment in mild climates runs longer; neglected equipment in extreme climates runs shorter.
Manufacturer parts warranties reflect similar expectations: compressor warranties from Carrier, Trane, Lennox, Rheem, and Goodman typically run 10 years from registration on current equipment, with some premium lines offering longer coverage — a useful proxy for how long a manufacturer itself expects the compressor to last without failing. The Department of Energy’s periodic minimum-efficiency updates (most recently the 2023 SEER2/HSPF2 change) also affect this indirectly: older, lower-efficiency refrigerants and parts become harder to source over time, which is part of why an aging R-410A system’s repair economics get worse as it ages, not just its mechanical wear.
What shortens HVAC lifespan
Lack of annual maintenance is the single biggest factor. A furnace heat exchanger that goes uninspected for 15 years fails faster than one cleaned and checked annually. Same with the AC: a coil that’s never cleaned accumulates biological growth that corrodes fins and restricts airflow.
Poor installation. A system that was improperly sized or installed without verifying refrigerant charge stresses its components from day one. Oversized AC systems short cycle (frequent on-off cycles), which wears out the compressor faster than a properly sized unit running longer, fewer cycles.
Extreme climate. Air conditioners in Phoenix run three times more annual hours than the same unit in Minneapolis. Heat pumps in cold climates work harder during heating season than the same unit in a moderate climate. Higher run hours mean earlier wear on motors, compressors, and electrical components.
Refrigerant issues. A system that runs low on refrigerant stresses the compressor. If this happens repeatedly without finding and fixing the leak, it shortens compressor life significantly.
The $5,000 rule
Use this formula when deciding whether to repair an aging unit: multiply the unit’s age in years by the cost of the repair. If the result exceeds $5,000, get replacement bids before approving the repair.
Examples:
| Situation | Math | Decision |
|---|---|---|
| $300 capacitor, 8-year-old AC | 8 × $300 = $2,400 | Repair it |
| $800 blower motor, 14-year-old furnace | 14 × $800 = $11,200 | Get replacement bids |
| $1,500 compressor, 10-year-old unit | 10 × $1,500 = $15,000 | Get replacement bids |
| $400 contactor, 12-year-old heat pump | 12 × $400 = $4,800 | Repair, borderline |
The formula is a threshold, not a verdict. Two adjustments to make:
Under warranty: do the repair regardless. A compressor still under manufacturer warranty (typically 5–10 years from registration) costs you labor only, not the $500–$800 part. Run the formula on the labor cost, not the full repair cost.
Multiple systems failing: consider replacement regardless. If a 15-year-old unit fails its capacitor in June, its blower motor in August, and a technician finds a refrigerant leak in September, the pattern is more important than any single repair cost. Parts failure clusters on aging equipment. A replacement bid is warranted even if each individual repair might pass the formula test.
Signs a unit is near end of life
Beyond the formula, watch for these patterns in an aging system:
- Increasing repair frequency. One repair every 3–4 years is normal for aging equipment. Repairs every season are not.
- Multiple components failing in the same cycle. See above.
- Escalating energy bills with no change in usage. A degraded coil, compressor running off-spec, or significant duct leakage can push utility bills 20–30% higher without any symptom obvious to the homeowner.
- R-410A refrigerant on a unit over 10 years old needing compressor work. R-410A is being phased out; service refrigerant pricing is rising. On an older unit needing a compressor, the refrigerant cost alone can tip the repair-vs-replace decision.
When to start getting replacement bids proactively
Don’t wait for a complete failure in August to start researching replacement. A failed compressor in peak cooling season means making a major purchase decision under pressure, with a hot house, in the contractor’s busiest month.
If your unit is more than 12 years old and has needed a repair this season, get one or two replacement bids now while the system is still limping along. That way you’re comparing options, not scrambling.
For what a replacement actually costs, see central air installation cost. For the repair cost context, see AC repair cost and AC compressor replacement cost. For what to ask a contractor before replacing anything, see The HVAC Quote Checklist. The complete HVAC cost index has all repair and replacement costs in one place.
When a system is near the end of these ranges, the next read is our new-system decision guide: how to time the replacement instead of letting a breakdown time it for you.
Age is only half the decision. A refrigerant leak on an older system is where it usually gets decided.
