An HVAC system rarely dies all at once. It gets louder, weaker, and thirstier for repairs, and your energy bills creep up while comfort drops. Knowing when to stop pouring money into an old unit — and what a new one costs — saves you from both a surprise breakdown in a heat wave and from over-repairing a system that is past its prime.
Signs it's time to replace
- Age. It is near or past the typical lifespan (see below).
- Repair frequency. You have called for service more than once or twice in the last couple of years.
- Rising bills. Energy costs climb even though your usage hasn't — a sign of lost efficiency.
- Uneven comfort. Rooms that never reach temperature, long run times, or short-cycling.
- A big-ticket failure. A dead compressor (AC) or cracked heat exchanger (furnace) on an old unit.
Typical HVAC lifespan
| System | Typical lifespan |
|---|---|
| Central air conditioner | 15–20 years |
| Gas furnace | 15–25 years |
| Heat pump | 10–15 years |
| Ductless mini-split | 15–20 years |
Repair or replace? The quick math
Two rules cut through it. The $5,000 rule: multiply the unit's age by the repair quote — if the result is over $5,000, lean toward replacing. A 12-year-old AC with a $450 repair is $5,400, so replacement is on the table. The 50% rule: if a repair costs more than half the price of a new system, replace instead. Both push you to stop sinking money into a unit near the end of its life.
What a new system costs in 2026
These are installed-cost ranges for a typical 2,000 sq ft home; your size, efficiency level, and region move the number:
| System | Typical installed cost |
|---|---|
| Central AC + furnace (full system) | $5,000–$11,000 |
| Central AC only | $2,500–$7,500 |
| Furnace only | $2,000–$5,400 |
| Heat pump | $3,800–$8,200 |
| Ductless mini-split | $3,000–$10,000 |
| Replace ductwork (add-on) | $1,400–$5,600 |
Get a ZIP-adjusted number for your home with the HVAC cost calculator, and if the replacement isn't an emergency, book it in the shoulder seasons (spring or fall) when installers are slower and prices soften — see the cheapest time of year for home projects.