Repair or replace?
The age, the repair quote and a replacement price. We do the per-year arithmetic and give you a straight call.
Average lifetimes we use
| System | Average life | Source |
|---|---|---|
| Gas tank water heater | 14.5 yrs | DOE Consumer Water Heaters TSD (2024), App. 8G |
| Electric tank water heater | 15.1 yrs | DOE Consumer Water Heaters TSD (2024), App. 8G |
| Heat pump water heater | 13 yrs | ENERGY STAR heat pump water heater assumptions (13 years) |
| Gas tankless water heater | 20 yrs | DOE Gas-fired Instantaneous Water Heaters TSD (2024), Table 8.3.5 |
| Gas furnace | 21.4 yrs | DOE Consumer Furnaces TSD (2023), App. 8G |
| Central air conditioner | 18–24.9 yrs | DOE Residential CAC & HP TSD (2016), Table 8.2.59 |
| Heat pump (ducted, outdoor unit + air handler) | 15.1–16.4 yrs | DOE Residential CAC & HP TSD (2016), Table 8.2.59 |
| Gas boiler | 26.9 yrs | DOE Consumer Boilers NOPR TSD (2023), Table 8.3.5 |
Guides by system
Common questions
How does the calculator decide?
It divides the repair price by the years the repair is likely to buy (the average life minus the unit’s age, never less than 2 years) and compares that with a new unit’s price divided by its full average life. Below 0.75 of the new-unit figure, repair; above 1.25, replace; in between, a toss-up.
What is the 50% rule?
A trade rule of thumb: if a repair costs more than half the price of a new unit, replace. A second version multiplies the repair price by the age in years and replaces when that beats the new price. We show both, but the per-year comparison is what drives the verdict.
Where do the average lifetimes come from?
From the Department of Energy’s technical analyses for its efficiency standards (water heaters 2024, furnaces 2023, central AC and heat pumps 2016, boilers 2023) and ENERGY STAR for heat pump water heaters. AC and heat pump lifetimes vary by climate, so your ZIP code changes them.
When should I ignore the math?
When safety is involved. A leaking tank cannot be repaired, and a cracked furnace heat exchanger can leak carbon monoxide. Those cases are flagged as replace regardless of the numbers.