The short version
Lean toward replacing your furnace if any of these are true:
- It is 15 or more years old and facing a significant repair. Older furnaces tend to fail again after the first major one.
- It is 20 or more years old. Even working, it is near the end of its life, and a single failure can leave you without heat in winter.
- You are already paying for another HVAC project, so a single permit and a single crew is more efficient than two separate trips.
- You are considering going electric, since a heat pump replaces both furnace and air conditioning and qualifies for rebates a new gas furnace does not.
- The repair is approaching half the cost of a replacement.
Lean toward repairing if:
- The furnace is on the younger side and the repair is small.
- It is a single, contained part failure on a system that is otherwise running well.
- You have a multi-year plan to go electric and want to nurse the furnace through the gap.
Seattle furnace lifespan
A furnace generally lasts somewhere in the range of fifteen to twenty-five years, and Seattle conditions tend to push toward the shorter end of that:
- Our damp climate is harder on the heat exchanger over time.
- Our long heating season means more run hours per year than warmer parts of the country.
- Short cycling in the shoulder seasons puts extra wear on components.
Higher-efficiency furnaces save on gas but have more complex parts, so they sometimes do not last quite as long as the simpler older units. The right balance for most Seattle homes is a solid mid-to-high-efficiency furnace.
The “half the cost” rule, applied in Seattle
The standard rule across the trade: if a repair costs about half of a replacement or more, replace. If you are staring at a major repair quote on a furnace that is already well into its life, replacement is usually the right call.
Two Seattle-specific adjustments:
If you are considering going electric anyway, use a lower threshold. The gas furnace’s remaining life is essentially zero in your long-term plan, so any major repair is money spent on an asset you are about to replace.
If your air conditioning also needs work, bundle. Doing a new furnace and AC together in one project is more efficient than doing them separately a year or two apart.
Repair signs that point toward replacing soon
Some failures predict more failures:
- A cracked heat exchanger. Replace right away for safety, since it is a carbon monoxide risk. On most furnaces it also signals end of life.
- Blower motor failure on an older furnace, especially when other parts are also showing wear.
- Control board failure on an older furnace, which often signals the end is near.
- Recurring short cycling, the system turning on and off every few minutes, which on an older furnace can be the start of cascading problems.
- Cleaning the flame sensor every single season, a sign the furnace is running marginal.
Repairs that do not mean “replace”: a one-time flame sensor cleaning, a capacitor replacement, or a thermostat replacement on a furnace that is otherwise healthy.
Should you skip the furnace and go heat pump?
For a lot of Seattle homeowners, this is the better path:
Rebates. A heat pump qualifies for the PSE rebate and the federal energy-efficiency tax credit. A new gas furnace gets no comparable incentives.
Lower operating cost. Heat pumps are generally cheaper to run than gas furnaces in Seattle’s mild climate, and the savings add up over the life of the system.
One system instead of two. A heat pump heats and cools. If you would otherwise be adding air conditioning anyway, a heat pump is the better whole project.
When a new furnace still makes more sense:
- You have a working air conditioner that is still fairly new and you do not want to waste it.
- The electrical work to support a heat pump is not in the budget right now.
- You are moving out of the home soon.
- Your home has placement or layout constraints that make an outdoor heat pump unit difficult.
For the broader decision, see furnace vs heat pump in Seattle.
