Definition — what 'end of life' actually means for a furnace
A modern condensing furnace's expected service life in the GTA is roughly 15–20 years. Older 80% AFUE mid-efficiency furnaces from the 1990s can push 25 years but at running costs a modern furnace would eliminate.
'End of life' shows up in three ways: (1) parts are no longer available or the compatible-part list is shrinking, (2) heat exchanger cracks or CO output exceeds safe limits, or (3) repeat repairs over 18 months exceed 50% of a replacement quote.
When repair is the right answer
Furnace under 12 years old, single component failure (inducer motor, ignitor, gas valve, flame sensor, pressure switch), no combustion-safety issue: repair is almost always correct. These are $150–$800 fixes on equipment worth $4,000–$6,000 to replace.
Furnace 12–18 years old, single component failure, no combustion-safety issue: repair is usually correct, but start planning for replacement in the next 1–3 seasons. Get proactive quotes in the shoulder season so you're not making the decision at midnight in January.
Failure modes — the four situations that push you toward replacement
First: a cracked heat exchanger. Combustion gases (including CO) can leak into the household air. Modern manufacturers cover heat exchangers 10–20 years, but the labour to swap one on an old furnace often approaches half the cost of a new furnace.
Second: repeated failures. Three service calls in one winter on the same furnace is a signal. Fourth calls typically don't come — the customer just calls to replace.
Third: efficiency mismatch. If you're running a 78% AFUE mid-efficiency furnace in a home you plan to keep 5+ years, replacing with a 95%+ AFUE unit typically pays back in fuel savings alone.
Fourth: an orphaned water heater. If the furnace was the only thing keeping the chimney warm enough for the atmospherically vented water heater, upgrading the furnace to sidewall PVC vent forces a water-heater decision at the same time.
Proof — how to pressure-test a replacement quote
Ask for the specific part number, the specific fault code, and — for a replacement quote — a Manual J heat-loss number. Any installer confident in their diagnosis will provide these without pushback.
Reject any 'today only' pricing. A furnace replacement decision at 10 pm in a cold house is not a decision — it's a stress response. Reputable Ontario installers will loan out space heaters and quote in the morning.
Action — what to ask Metroheat on the call
When you call Metroheat at (416) 283-5698, describe the symptom (what the furnace is doing / not doing), the age of the equipment if you know it, and whether there's any burning smell or CO alarm activity. That information triages the call — a CO alarm gets a same-day dispatch; a cold house on a mild day gets scheduled at the earliest available slot.
Every diagnostic gets a written summary: symptom, fault code, root cause, part cost, labour cost, and — if applicable — a repair-vs-replace comparison you can take away and think about.