How long does a furnace last?

How long a furnace lasts

Published service life: 15–25 years. Roots plans for: year 20.

Service life is a planning horizon, not an expiry date. It tells you when to start budgeting, get a second quote, and stop paying for repairs on something near the end — not the day it stops working.

What changes this

A cracked heat exchanger, not age, is what usually ends a furnace. It is a carbon monoxide hazard and a condemned unit, so the annual inspection matters more here than the calendar does.

Sources

• InterNACHI's Standard Estimated Life Expectancy Chart for Homes, cross-checked against the NAHB/Bank of America Study of Life Expectancy of Home Components (February 2007) (Furnaces (gas 18, electric 15, oil 20)).

Service-life figures are typical estimates drawn from published industry references. Where a second reference covers the component, the figure is cross-checked against it and any disagreement is set out above; where only one reference covers it, that is stated. Actual life varies with installation, water quality, climate, and maintenance, and these figures shouldn't be relied on for insurance, lending, or warranty decisions.

Maintenance is what decides where in the range you land

The published range is wide for a reason: two identical units, installed the same day, routinely fail years apart. What separates them is upkeep.

For a furnace, the tasks that matter most:

• Replace HVAC air filter — Clogged filters strain the blower and can overheat the furnace. 1" filters may need monthly changes.
• Schedule furnace tune-up — Annual service prevents mid-winter failures and catches cracked heat exchangers (a CO hazard).

Roots tracks the age of every component in your home alongside the upkeep that extends it, so the replacement is a planned expense instead of an emergency.