Heating and cooling equipment rarely fails without warning, but it does wear out, and replacing it before a midwinter breakdown gives you time to choose well. How long it lasts depends on the type, how hard it works and how well it's maintained.
The DOE puts a central air conditioner's life at 15 to 20 years. ENERGY STAR suggests considering replacement when a heat pump or air conditioner is more than 10 years old, or a furnace or boiler more than 15, especially if it needs frequent repairs and your bills are rising.
HVAC Lifespan & Repair-vs-Replace Calculator
Your system's age against ENERGY STAR and DOE guidance.
Lifespan and replacement signals
The first column is the typical service life the DOE gives for that equipment; the second is the age at which ENERGY STAR suggests you start comparing options. An "n/a" means that source does not state a figure for that type, not that none exists.
| Equipment | Typical life (DOE) | Consider replacing at (ENERGY STAR) |
|---|---|---|
| Central air conditioner | 15 to 20 years | 10 years |
| Room air conditioner | 10 to 15 years | n/a |
| Heat pump | n/a | 10 years |
| Gas furnace | n/a | 15 years |
| Gas or oil boiler | n/a | 15 years |
| Storage water heater | 10 to 15 years | over 10 years |
| Tankless water heater | about 20 years | n/a |
| Heat pump water heater | 10 to 15 years | n/a |
| Solar water heater | about 20 years | n/a |
The water heater rows come from the DOE's water heater comparison; a heat pump water heater lasts 10 to 15 years and a solar system about 20, the same as a tankless unit. For more on which part fails and when a tank is worth fixing, see how long a water heater lasts.
ENERGY STAR's age signals are prompts to compare options, not deadlines: a well-maintained system can run longer, and newer equipment is much more efficient. ENERGY STAR says an ENERGY STAR furnace is 15% more efficient than a conventional one, and an ENERGY STAR boiler 5% more efficient than a new standard model.
Signs it's time to replace
ENERGY STAR lists these signals:
- Frequent repairs and rising energy bills.
- Rooms that are too hot or too cold.
- Humidity problems, too dry in winter or too humid in summer.
- Excessive dust, which can come from leaky ducts.
- A noisy system.
What shortens an HVAC system's life
Two systems of the same age can be years apart in wear, because run hours and strain, not just the calendar, decide when equipment gives out. A few causes do most of the damage.
Oversizing is the quiet one. An oversized AC or furnace satisfies the thermostat fast, then shuts off, so it cycles on and off many times an hour. Every start is the hardest moment on a compressor or an igniter, so more cycles mean more wear, and the short runtimes also leave humidity in the air.
Skipped maintenance works the same way through heat. A clogged filter or a dirty coil forces the blower and compressor to run harder and hotter, and heat is what ages motors and electronics.
Where the unit lives matters too. Salt air on the coast corrodes an outdoor unit's aluminum fins and cabinet, so coastal systems can degrade faster than identical units inland. A system in a hot climate that runs most of the year simply accumulates run hours faster, which is part of why a heat pump, heating and cooling, tends to wear sooner than a cooling-only AC of the same build.
Hard water does the equivalent to a water heater. Dissolved minerals drop out as scale on the tank bottom and the heat transfer surface, which insulates it and makes the burner or element run longer, and the harder the water the faster the anode and tank corrode.
Repair or replace?
Compare a repair quote with a replacement quote for your home. A common contractor rule of thumb is to replace when a repair would cost more than about half the price of a new system, especially on older equipment; it's a rule of thumb, not a standard. Weigh in the equipment's age against the signals above, how efficient it is, and whether its refrigerant is still supported; see the refrigerant phase-out.
Work the rule through on age rather than on a specific price. The rule compares the repair quote against what a new system would cost, as a share of that new price.
If a repair would cost more than half of a replacement on an older unit already past the ENERGY STAR 10-year signal, that is above the half-price line, so replacement is the stronger call. If the same repair is only a small fraction of a new system on a much younger unit, it falls well under the line and fixing it wins.
Before you apply any of these signals, confirm how old the unit actually is. The nameplate date can be missing or wrong, so decode the serial number with the HVAC serial number decoder to get the real manufacture date.
Making equipment last
- Change filters on schedule; clogged filters overwork the blower and can overheat a furnace.
- Keep the outdoor unit clear and the coils clean.
- Get a pre-season tune-up, the cooling system in spring and the heating system in fall, as ENERGY STAR recommends; see HVAC maintenance cost.
- Fix duct leaks, which make the system run longer.
Frequently asked questions
How long does an air conditioner last?
A central air conditioner lasts 15 to 20 years, according to the DOE, and a room unit 10 to 15.
When should I replace my furnace?
ENERGY STAR suggests considering it when a furnace is more than 15 years old, needs frequent repairs, or your bills are rising.
Is it worth repairing a 15-year-old AC?
For a minor, inexpensive repair, often yes. For a major one, compare it with a replacement quote; a new system is more efficient and comes with a fresh warranty.
How long do heat pumps last?
ENERGY STAR suggests considering replacement after 10 years, since newer models are more efficient; many run longer with good maintenance.
How long does a gas boiler last?
ENERGY STAR suggests considering replacement once a boiler is more than 15 years old, the same signal it gives for furnaces. A well-maintained boiler can run past that, so treat 15 years as a prompt to compare options rather than a hard expiry.
How long do mini splits last?
A ductless mini split is a type of air-source heat pump, so ENERGY STAR's 10-year heat pump replacement signal applies to it. A well-maintained unit can run past 10 years, so use that age as the point to start weighing replacement against rising repair costs.
Does a heat pump last as long as an AC?
ENERGY STAR gives a heat pump and an air conditioner the same 10-year replacement signal, even though the DOE puts a central AC's typical life at 15 to 20 years. A heat pump both heats and cools, so it runs far more hours a year than a cooling-only AC, and those extra run hours are why the shorter signal makes sense.
What is the average age of a system that fails?
The DOE and ENERGY STAR do not publish a single average age at which systems fail. They give ranges instead, 15 to 20 years for a central AC and 10 to 15 for a room unit or water heater, with replacement signals at 10 years for heat pumps and ACs and 15 for furnaces and boilers. Frequent repairs and rising bills are better warnings than age alone.
Sources & References
- ENERGY STAR: When is it time to replace? (10 and 15 years; replacement signals)
- U.S. DOE: Energy Saver 101, Home Cooling (PDF), central AC 15 to 20 years, room AC 10 to 15
- U.S. DOE: Energy Saver Guide (PDF), water heater lifespans
- U.S. DOE: Which water heater is right for you? (lifespans by type)
- ENERGY STAR: Heat pump water heater fact sheet (replace a tank over 10 years old)