Two numbers settle most repair-or-replace arguments, and neither one is the number your technician just quoted you.
Multiply the system's age in years by the repair estimate. If that number is over $5,000, replacement usually wins. Separately, if the repair costs more than half of what a new system would cost, replacement usually wins too. Contractors have used both rules for years because they work often enough to be useful.
They still miss two things that matter. A cracked heat exchanger is not a repair decision at all, it is a safety decision, and it ends the conversation regardless of what the math says. And on an aging R-22 or first-generation R-410A system, the refrigerant itself is now expensive enough that a "small" leak repair can quietly blow past the $5,000 threshold before a wrench is even turned.
Direct answer
Get the specific failed component named, get a written repair-only estimate, and run both rules of thumb before you decide anything. Then check two things the rules do not cover: whether the failure is a cracked heat exchanger (replace, full stop, for safety) and whether the system runs R-22 or older R-410A equipment (price the refrigerant separately, because that cost can change the answer). If the furnace is healthy and under about 10 to 12 years old but the AC has failed, price a dual-fuel heat pump conversion before a like-for-like AC swap. It often costs little more and removes a second replacement decision later.
The age-and-cost decision table
DOE and AHRI-derived average product-lifetime assumptions put central air conditioners around 15 years and gas furnaces around 18 years, and ENERGY STAR guidance suggests weighing replacement once equipment passes 10 to 15 years old. Neither number is a deadline. It is a point where a major repair on that specific unit gets harder to justify.
| Air conditioner age | Recommendation | Why |
|---|
| 0 to 8 years | Repair almost any failure | This early, a compressor or coil failure more often points to an installation, charge, or maintenance problem than end-of-life wear |
| 9 to 12 years | Repair isolated failures (capacitor, fan motor, control board, TXV); get a replacement quote before authorizing a compressor or coil job | Puts a real number next to the age-times-cost rule before you commit |
| 13 to 15 years | Repair only inexpensive parts; run both rules of thumb on anything bigger | A second major failure inside 12 months is the signal to stop repairing |
| 16+ years | Plan replacement now | Past typical service life, and often still running R-410A equipment from before the 2025 manufacturing cutoff described below |
| Furnace age | Recommendation | Why |
|---|
| 0 to 12 years | Repair almost any failure (ignitor, blower motor, inducer motor, control board) | Well inside typical service life |
| 13 to 18 years | Repair inexpensive parts; treat a cracked heat exchanger as a hard stop regardless of age | See the safety section below |
| 19+ years | Plan replacement | Past the median service life estimate, and parts for discontinued models often thin out here too |
2026 repair costs by failure, and the keep-or-kill call
These are national ranges from HVAC cost-tracking sites (Angi, HomeGuide, Today's Homeowner), checked September 2026 and cross-checked across at least two sources per line. Your contractor's number depends on tonnage, furnace stage, brand, and local labor rates.
| Failure | Typical system | 2026 cost range | Keep or kill |
|---|
| Capacitor or contactor | AC | $150 to $400 | Always repair. Cheap, fast, rarely a sign of anything bigger on its own |
| Condenser fan motor | AC | $200 to $700 (up to $1,200 for ECM motors) | Repair unless it is the second major AC failure in a year |
| TXV (expansion valve) | AC | $250 to $850 | Repair on a system under about 12 years old; weigh against the compressor line below on older systems, since a failing TXV can be an early compressor-stress signal |
| Evaporator coil leak | AC | $250 to $1,800 to patch; $600 to $4,500 for full coil replacement depending on warranty coverage | Patch on a younger system; a full coil replacement on a system past 10 to 12 years is close enough to the 50% rule that it deserves a real replacement quote first |
| Compressor | AC | $1,500 to $3,500 installed, more on larger tonnage | The single biggest trigger for the age-times-cost rule. Run the math before authorizing |
| Control board | AC or furnace | $300 to $1,200 | Repair in most cases; check parts availability first on a discontinued model |
| Ignitor | Furnace | $100 to $250 | Always repair |
| Inducer motor | Furnace | $400 to $1,100 | Repair unless it is stacking with another major failure |
| Blower motor | Furnace | $500 to $2,300 | Repair on a furnace under about 15 years old; weigh against replacement on older units |
| Cracked heat exchanger | Furnace | $1,250 to $3,000 to replace the part alone, where a shop will even attempt it | See the hard stop below. Most contractors will not repair a cracked exchanger; they will recommend replacing the furnace |
The hard stop: a cracked heat exchanger is not a repair decision
A furnace heat exchanger separates the combustion gases, including carbon monoxide, from the air that circulates through your house. A crack in it can let combustion gas leak into that airstream. The Consumer Product Safety Commission's Carbon Monoxide Information Center names fuel-burning heating equipment as a leading source of the non-fire carbon monoxide deaths it tracks every year.
A cracked heat exchanger cannot be safely repaired. The standard response is to replace the exchanger, which on many furnaces costs close to a full replacement once labor is counted, or to replace the furnace outright. Do not let anyone talk you into "just running it" or patching it. If a technician tells you the heat exchanger is cracked, ask to see the crack (a borescope photo, not just a verbal claim) or the combustion-analyzer reading that led to the call, then treat replacement as settled and move to comparing furnace-only replacement against a heat pump conversion.
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Refrigerant status in 2026, and why it changes the math
The standard repair-or-replace rules assume refrigerant is a minor line item. That stopped being true for older systems.
| Refrigerant | Status in 2026 | What it means for a repair decision |
|---|
| R-22 (most systems installed before roughly 2010) | Production and import banned in the US since January 1, 2020. Legal to keep running and to service with reclaimed refrigerant; no forced retirement | A leak repair plus a recharge can run $100 to $300 per pound in 2026 on top of the repair labor, since no new R-22 is being made. A "small" leak fix on an R-22 system can push the total past the $5,000 age-times-cost threshold by itself |
| R-410A (most systems installed roughly 2010 to 2025) | Legal to service, and not scarce. New residential split-system air conditioners and heat pumps using R-410A stopped being manufactured or imported for the US market as of January 1, 2025 under EPA's Technology Transitions Rule. A planned January 1, 2026 installation cutoff for existing pre-2025 stock was reconsidered and lifted, effective July 27, 2026, so contractors can still install unsold pre-2025 R-410A equipment while supplies last | Repairs remain routine and refrigerant is not yet expensive, but this is now the last generation of R-410A equipment. Ask whether replacement parts are still stocked before authorizing a major repair on an older unit |
| R-32 and R-454B | Standard refrigerants on new 2025-and-later residential equipment, with global warming potential of 675 and 466 versus R-410A's 2,088 | Only relevant when you are pricing new equipment, not to what is already installed in your house |
Some state rules are stricter than the federal posture. New York, for example, kept its own January 1, 2026 installation deadline for R-410A equipment in place. Check your state and local code before assuming the federal reconsideration applies to your permit.
Don't let a tax credit set your timing
The federal 25C Energy Efficient Home Improvement Credit, the one behind years of "30% back, up to $2,000" heat pump math, does not apply to equipment placed in service after December 31, 2025. If a contractor's replace-now pitch leans on a 2026 federal credit, ask for the current IRS citation. There is not one. Full details are in heat pump tax credit 2026. A repair-or-replace decision should rest on the equipment, the safety finding, and the arithmetic above, not on an incentive that expired.
The dual-fuel middle path
If the furnace is the healthy half of the pair, replacing the AC does not have to mean a like-for-like AC. A heat pump outdoor unit and matching coil can go where the failed AC was, using the existing furnace's blower and ducts, with the furnace kept as backup heat below a set outdoor temperature (commonly in the 30 to 40°F range, sometimes lower on modern cold-climate equipment). Manufacturers describe this as a dual-fuel or hybrid system, and it runs on electricity most of the year while the furnace only fires in the coldest stretches.
This is worth pricing specifically when the furnace is under roughly 10 to 12 years old, 90%+ AFUE, and has no open problems of its own. Scrapping a furnace with a decade of life left to buy a single-fuel heat pump throws away a working asset; adding the heat pump to it does not. Compare the incremental cost against a straight AC replacement using the backup heat guide for how the switchover point and controls work, and the panel upgrade guide for whether the electrical side adds cost.
A furnace already past 13 to 18 years narrows this option. You would be pairing new heat pump equipment with a furnace that may itself need replacing in a few years, which is closer to the whole-home conversion case below than a dual-fuel bridge.
An illustrative cost comparison
These are round numbers built from the ranges sourced above and this site's own previously sourced installed-cost bands, not a real customer's quote. Use it to see how the pieces stack, then run your own numbers with a written estimate in hand.
A 14-year-old 3-ton AC's compressor fails. The furnace is 16 years old, standard 80% AFUE gas, with no current problems. A repair estimate comes in around $2,400.
- Age-times-cost check: 14 years x $2,400 is $33,600, well past the $5,000 threshold. The rule of thumb says replace.
- Repair now, replace later: $2,400 today, then a like-for-like AC-and-furnace replacement in a few years at a national average of roughly $5,000 to $12,500 (commonly cited around $7,500), for a rough total near $9,900 to $14,900 spread across two projects, two truck rolls, and two permits.
- Replace with a heat pump now: this site's own sourced band for a ducted whole-home heat pump conversion using existing, usable ducts is $12,000 to $18,000 installed, from heat pump buying guide. One project instead of two, and it resolves the furnace's own aging clock at the same time, which a straight AC-only replacement does not.
- Where the heat pump does not clearly win: if the furnace were 8 years old instead of 16, dual fuel would only replace the failed AC side, likely landing closer to a straight AC replacement cost plus a moderate premium for the coil and controls, without touching a furnace that still has a decade of life in it.
Red flags in a repair-or-replace conversation
- A technician recommends full replacement without naming the specific failed part or handing you a written repair-only estimate to compare it against.
- A refrigerant recharge quote does not state the price per pound or how many pounds the system takes, which matters most on R-22 systems.
- Nobody asks the furnace's age or AFUE before quoting an AC-only replacement, which skips the dual-fuel option entirely.
- A "cracked heat exchanger" claim arrives with no photo, borescope image, or combustion-analyzer reading behind it.
- The only replacement option offered is a single brand with no dual-fuel or heat-pump-conversion alternative priced.
- Same-day pressure to sign during a comfort emergency, before you can get a second opinion on a five-figure decision.
If your AC alone is the problem and a heat pump is not on the table for you, our sister site's AC repair or replace guide walks the cooling-only version of this decision in more depth.
Frequently Asked Questions
Is it ever worth repairing a 15-year-old AC?
Sometimes, for a cheap, isolated failure like a capacitor or fan motor. Run the age-times-cost rule on anything bigger: 15 years times a $2,000 compressor repair is $30,000, well past the $5,000 threshold, so a major repair at that age is usually the wrong call.
Can I repair a cracked heat exchanger instead of replacing the furnace?
Most contractors will not attempt it. A cracked exchanger is a carbon-monoxide safety issue, not an ordinary wear item, and the standard response is to replace the exchanger or the furnace rather than patch it. Ask to see the evidence behind the diagnosis, then treat replacement as settled.
Why does my R-22 system's leak repair cost so much more than it used to?
Because no new R-22 has been produced or imported into the US since January 1, 2020. Reclaimed refrigerant now runs $100 to $300 per pound in 2026, so a routine leak-and-recharge job costs far more than the labor alone.
Can I keep my furnace and just add a heat pump?
Often yes, if the furnace is healthy and roughly 10 to 12 years old or newer. This is called a dual-fuel or hybrid system: a heat pump handles most of the heating and cooling, and the furnace kicks in as backup below a set outdoor temperature. It is worth pricing before you scrap a furnace that still has years of life left.
Does the 2026 federal tax credit make replacing now a better deal?
No. The 25C credit behind that math does not apply to equipment placed in service after December 31, 2025. Do not let a stale incentive push the timing of a decision that should rest on the equipment and the arithmetic above.
Where to go next
- Get a written, itemized repair estimate naming the specific failed part, then run both rules of thumb above before you sign anything.
- If you are leaning toward a heat pump conversion, size the project with real cost of a heat pump and check whether a furnace could stay in the picture with the backup heat guide.
- If a heat pump is not in scope and your AC alone is the problem, see the cooling-only version of this decision at aircondition.guide.
- Once you have a written heat pump proposal in hand, send it for a free quote review before the deposit.
What we could not verify
- The exact DOE technical support document behind the 15/18-year lifetime averages. The age bands are reported consistently across independent manufacturer and contractor sources and align with ENERGY STAR's 10 to 15 year replacement guidance, but we did not retrieve the underlying DOE technical support document directly in this pass, so we are not citing a specific document number.
- A universal repair-cost threshold. The $5,000 and 50% rules are widely used heuristics, not laws of physics. They say nothing about a refrigerant type going obsolete mid-system or a safety failure, which is why this page adds those two corrections rather than treating the rules as complete on their own.
- Your specific repair or replacement price. Every range above is a national estimate. Tonnage, furnace stage, brand, ductwork, electrical scope, and local labor rates all move the real number. Get a written, itemized estimate for your actual equipment.
- State and local code deviations from the federal R-410A installation posture. We confirmed New York kept its own 2026 deadline; we did not check every state, so ask your contractor which rule applies in your permit jurisdiction.
Sources
All primary sources retrieved and checked September 1, 2026.
