When a major appliance breaks, you face one question: fix it or replace it? Get it wrong one way and you pour money into equipment that fails again next year. Get it wrong the other way and you replace something that had years of life left. Here's a practical framework, plus the specific failures that usually tip the decision.
Know the typical lifespan
Age is the biggest factor. These are typical ranges for well-maintained equipment. Your climate, usage and installation quality all shift them.
| Equipment | Typical lifespan |
|---|---|
| Central air conditioner | 12 – 17 years |
| Heat pump | 10 – 15 years |
| Gas furnace | 15 – 20+ years |
| Tank water heater (gas or electric) | 8 – 12 years |
| Tankless water heater | 15 – 20 years |
Ranges are general industry estimates. Your equipment's manufacture date is usually on its data plate, often encoded in the serial number.
Two quick rules of thumb
The 5,000 rule (HVAC). Multiply the unit's age in years by the repair cost. If the result is over 5,000, replacement is usually worth pricing out. A 12-year-old AC with a $700 repair gives 8,400, so get a replacement quote. A 5-year-old AC with the same repair gives 3,500, so repair it.
The 50% rule (any appliance). If the repair costs more than half the price of a new unit and the equipment is past the middle of its lifespan, replacement usually makes more sense.
These are starting points, not laws. A 14-year-old furnace that needs a $150 igniter should get the igniter.
Air conditioners: failures that usually mean replace
- Compressor failure on an older unit. The compressor is the most expensive component. On a unit near or past 10–12 years, the repair often approaches the cost of a new condenser.
- An R-22 system with a refrigerant leak. U.S. production and import of R-22 ended on January 1, 2020. Existing systems can still be serviced with recycled or stockpiled R-22, but it's expensive. A leaking R-22 system is usually a replacement candidate.
- Repeated refrigerant leaks. Topping off refrigerant without fixing the leak is a recurring cost, not a repair.
Usually worth repairing: capacitors, contactors, fan motors, thermostats, a clogged condensate drain and minor electrical faults. These are common, relatively cheap fixes. Price a specific part with our AC repair cost calculator.
Furnaces: failures that usually mean replace
- A cracked heat exchanger. This can allow carbon monoxide into your home. Repairs are costly, and on most older furnaces replacement is the recommended and safer route. Ask the technician to show you the evidence, such as photos or camera footage, and get a second opinion given the cost.
- Frequent breakdowns in the last few years on a unit near the end of its lifespan.
Usually worth repairing: igniters, flame sensors, blower motors on newer units, inducer motors, pressure switches and control boards on furnaces with years left. Our furnace repair cost calculator shows typical prices for each part, and this guide covers the most common no-heat causes.
Water heaters: failures that usually mean replace
- A leak from the tank itself. Once the tank is corroded through, it can't be repaired.
- Rusty hot water on an older tank, which often means internal corrosion.
- Age past about 10 years combined with any significant repair.
Usually worth repairing: heating elements and thermostats on electric heaters, thermocouples and gas valves on gas heaters, and a leaking drain valve or relief valve. These are inexpensive fixes on a younger tank.
Other factors to weigh
- Energy efficiency. New AC and heat pump systems are generally much more efficient than units from 15 years ago. Lower bills offset part of the replacement cost over time.
- How long you'll stay. If you're selling within a year or two, a reasonable repair may be the better financial choice.
- Refrigerant changes. New residential AC systems have been shifting to lower-impact refrigerants such as R-454B and R-32. Mixing old and new components isn't possible, so replacing only the outdoor unit of an older split system may not be an option. Ask your contractor.
- Rebates. Utilities and states often offer rebates for high-efficiency equipment. Check your utility's website before you buy.
How to get an honest recommendation
Ask the technician for both numbers: the repair cost and the replacement cost, in writing. Ask what they'd do if it were their own home. For any replacement recommendation over a few thousand dollars, get a second opinion. It's standard practice, and our guide to comparing quotes can help.
Frequently asked questions
How much does an AC or furnace repair usually cost?
See our HVAC repair cost calculator for typical ranges by system and severity.
How much does a new water heater cost?
Our plumbing cost calculator shows typical installed ranges for standard tank and tankless replacements.
Can regular maintenance extend lifespan?
Yes. Changing HVAC filters, annual tune-ups and flushing a water heater yearly all help. See our seasonal maintenance checklist.