Use this repair or replace calculator to check whether fixing your AC, heat pump or furnace still makes sense. Enter the system’s age, the repair quote and a replacement price, and it runs the rules of thumb that HomeGuide, This Old House and ENERGY STAR use.
Rules and prices checked on November 4, 2026. Keep in mind that the calculator is a decision aid, not a diagnosis, so get a written quote before you decide.
Repair or replace calculator
How the repair or replace calculator works
In short, the calculator runs up to six checks and counts how many point to replacing. So if none do, repairing looks like the better value. If one does, it’s a close call. But if two or more do, replacing is likely the better value. That count is our own simple summary, so read each check as well.
| Check | What it looks at | Source |
|---|---|---|
| 50% rule | Replace if the repair costs 50% or more of a new system | HomeGuide |
| $5,000 rule | Replace if the age in years × the repair cost is more than $5,000 | HomeGuide; This Old House |
| 30% rule | Repair if the system is under 10 years old and the repair is 30% or less of the replacement cost | This Old House |
| Age | Consider replacing an AC or heat pump over 10 years old, or a furnace over 15 | ENERGY STAR |
| R-22 | Replace an AC or heat pump that still uses R-22 refrigerant | HomeGuide; This Old House |
| Frequent repairs | Replace a system that keeps breaking down | HomeGuide; ENERGY STAR |
For example, take a 12-year-old central AC with a $900 repair quote and the $8,460 average replacement cost. The repair is about 11% of a new system, so the 50% rule says repair. However, 12 × $900 = $10,800, which is well over $5,000. The AC is also past ENERGY STAR’s 10-year mark. As a result, two checks point to replacing.
Default replacement costs in the repair or replace calculator
If you don’t have a replacement quote yet, the calculator starts with the national averages from a 2026 This Old House survey of 1,000 homeowners. Of course, you can overwrite the default with your own number at any time.
| System | Average replacement cost |
|---|---|
| Central air conditioner | $8,460 |
| Air-source heat pump | $8,007 |
| Gas furnace | $8,533 |
| Electric furnace | $6,892 |
| All HVAC systems | $8,209 |
For a price based on your home’s size and system type, try our HVAC replacement cost calculator instead. Then subtract any rebate you qualify for before you enter the number.
How old is too old?
Age alone doesn’t decide it, but it helps. Specifically, HomeGuide gives these typical lifespans, and the calculator shows the one for your system next to the result.
| Equipment | Typical lifespan |
|---|---|
| Furnace | 15–30 years |
| Central AC | 15–20 years |
| Heat pump | 10–20 years |
Other sources are more cautious about air conditioners, though. Both This Old House and Angi put a central AC at about 12 to 15 years. For more detail, read our guides to how long an AC lasts and how long a furnace lasts.
What to do when it’s a close call
- Get a written diagnosis and repair quote, plus a replacement quote to compare.
- Rule out simple problems first with our AC not cooling and furnace blowing cold air guides.
- Then think about running costs. ENERGY STAR says a properly installed ENERGY STAR heat pump or AC can save up to 20% on heating and cooling.
- Also consider refrigerant costs. AHRI and the Alliance told ACHR News that refrigerant prices are likely to rise, which could make leak repairs on R-410A systems pricier.
- Read our full guide on whether to repair or replace HVAC for the warning signs to watch for.
Repair or replace calculator FAQ
What is the $5,000 rule for HVAC?
First, multiply the system’s age in years by the repair cost. If the result is more than $5,000, HomeGuide and This Old House both suggest replacing. For instance, a $450 repair on a 12-year-old AC gives $5,400.
Is it worth fixing a 15-year-old furnace?
It can be. After all, HomeGuide puts furnace lifespans at 15 to 30 years. Still, it suggests replacing a furnace older than 15 if it breaks down often or the repair costs more than half the price of a new one.
Should I replace my AC and furnace at the same time?
Often, yes, when both are aging. HomeGuide suggests replacing both together if the furnace is more than 15 years old. Our guide on replacing the AC and furnace at the same time covers the costs.
Does the repair or replace calculator include rebates?
No, so subtract any rebate from the replacement cost yourself. Our heat pump rebate finder lists programs by state.
Sources and review
Sources: HomeGuide, AC repair cost; HomeGuide, furnace replacement cost (December 31, 2025); HomeGuide, HVAC cost (August 27, 2025); This Old House, HVAC replacement cost (September 2, 2026); This Old House, AC repair cost (March 16, 2026); This Old House, evaporator coil replacement cost (April 6, 2026); Angi, replacing heat and AC at the same time; ENERGY STAR, when is it time to replace?; ACHR News, EPA removes R-410A installation deadline (May 21, 2026). All checked on November 4, 2026.
Written by: HVAC Switch. Last updated: November 4, 2026. Read our editorial policy to learn how we research prices, or contact us if you spot an error.