System guide: heating and cooling
Gas Furnace: typical service life and when to plan
A furnace typically lasts 15 to 20 years on the published range. What moves that number, how it stops, and the year to put on your calendar.
InspectedOctober 16, 2026figures as pulled
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The typical range
15 to 20 years
That is the typical service life for a furnace on the published range. It is a range for the type, not a promise about the unit in your house. Some run well past the far end; some stop short of the near end.
Range source: click-4-coverage.com SYSTEMS table (src/lib/systems.ts, main, read 2026-10-16). Category: Heating and cooling.
Independent figure: InterNACHI chart: Furnace: 15 to 25 years (undated); NAHB 2007: Furnaces: 15 to 20 years (HVAC table); Furnaces, Warm-Air, Gas: 18 years (appliance table). It matches the published range.
The biggest lever
Filter discipline and annual service. The filter is the cheapest part of the system and the one that does the most to protect the rest of it. A clogged filter starves the blower and the heat exchanger of air, and the furnace works harder every hour it runs. An annual service visit catches what a filter cannot.
On your walk-through
- Pull the filter, read its size off the frame, and buy spares.
- Find the data plate inside the front panel and write down the model and serial number.
- Check that the vent pipe leaving the furnace is connected and supported along its run.
How it stops, in plain words
Failure mode: Seasonal
It works hardest in one season, so trouble tends to show up in the first hard week of that season, when every technician in town is booked. Testing it a few weeks before the season turns is the whole point of the fall and spring checklists.
When to plan: a date, not a symptom
Do not wait for a noise or a puddle to start thinking about a furnace. Work it out from the install year instead. Add 15 to the year it went in: that is the year the typical range opens, and the year to price it, budget for it and decide what you would do. Add 20: that is the year the range closes.
Put the opening year on your calendar today. Age is a planning input, not a diagnosis, and nothing on this page says your unit will stop in any given year.
| Installed | Age in 2026 | Range opens | Range closes | Where 2026 falls |
|---|---|---|---|---|
| 2000 | 26 | 2015 | 2020 | past the far end of the range |
| 2005 | 21 | 2020 | 2025 | past the far end of the range |
| 2010 | 16 | 2025 | 2030 | inside the range |
| 2015 | 11 | 2030 | 2035 | before the range opens |
| 2020 | 6 | 2035 | 2040 | before the range opens |
| 2024 | 2 | 2039 | 2044 | before the range opens |
Arithmetic only: install year plus 15, install year plus 20, and 2026 minus the install year. No other figure is used.
If you cannot find the install year
Look for a data plate or label on the unit. Many carry a manufacture date, or a serial number that encodes one; the maker's site or a technician can decode it. Until you have a date, write the age down as unknown rather than guessing, and ask for it to be read at the next service visit.
The heating side of the house gets its own pre-season list: the fall furnace walk-through.
Same category on the index
- Boiler: 15 to 25 years
- Ductless Mini Split: 10 to 20 years
- Central Air Conditioner: 12 to 17 years
- Heat Pump: 10 to 16 years
Back to the full index, all 18 systems · How the ranges are sourced