Typical furnace replacement costs in London
Mature neighbourhoods on heavy clay soil, with big lots and a deep bench of local contractors. London homes are overwhelmingly forced-air gas — a straightforward like-for-like swap keeps costs at the low end unless ductwork needs attention.
| Project | Typical range | Notes |
|---|---|---|
| Gas furnace, mid-efficiency | $3,500–$5,500 | 80% AFUE single-stage; the budget replacement for a like-for-like swap |
| Gas furnace, high-efficiency | $5,000–$8,500 | 96–98% AFUE two-stage or modulating; lower gas bills, PVC venting |
| Furnace + central AC combo | $8,000–$13,900 | Full system replacement with existing ductwork; bundled pricing beats doing them separately |
| Central AC replacement only | $4,000–$8,000 | Matched to your existing furnace; SEER2 rating drives the range |
| Annual tune-up / service call | $150–$350 | Yearly maintenance that keeps the warranty valid and catches failures early |
What moves the price in London
- Efficiency rating (AFUE) — a 96% furnace costs more upfront but saves roughly $280+/year on gas versus an 80% unit in a typical Ontario home.
- Venting changes — upgrading from an 80% chimney-vented furnace to 90%+ high-efficiency needs new PVC venting through a wall ($300–$600).
- Home size and BTU sizing — bigger isn't better; an oversized furnace short-cycles, wastes gas, and wears out faster.
- Ductwork condition — leaky or undersized ducts kneecap a new furnace; modifications add $500–$2,000.
- Timing — a planned October replacement beats a January emergency call, which can carry a 20–50% premium.
Local notes for London homeowners
- London's clay soil expands and contracts with moisture — drainage and base work are critical, not upsells.
- Mature tree canopy is protected in many areas; root zones complicate excavation and planting plans.
- Post-war bungalows dominate many streets — small bathrooms and single-car driveways are the typical scope.
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Furnace Replacement Cost in London: FAQ
How much does a furnace replacement cost in London?
In London, a mid-efficiency gas furnace runs $3,500–$5,500 installed, and a high-efficiency (96%+ AFUE) unit $5,000–$8,500. Replacing the furnace and central AC together typically costs $8,000–$13,900. London's competitive local market keeps quotes near the middle of these ranges; clay-soil drainage work is the common add-on.
Should I repair or replace my furnace in London?
If it's 15+ years old, needs a repair over $500, or your gas bills keep climbing, replacement usually wins — especially going into winter. A cracked heat exchanger is an automatic replace: it's a carbon monoxide risk and the part alone runs $1,200–$2,500+. In London, a furnace that quits in January is an emergency call at emergency rates — October is when you replace on your schedule, not the weather's.
What size furnace does my London home need?
Roughly 60,000–80,000 BTU for a 1,500 sq ft bungalow, up to 100,000–120,000 for a 3,000 sq ft two-storey — but a proper heat-loss calculation beats rules of thumb. Oversizing is the most common and most expensive mistake: short cycling, uneven heat, early failure. London's post-war bungalows keep scopes small and predictable.
Do I need a permit to replace a furnace in London?
Yes — Ontario municipalities require permits for furnace replacement, typically $100–$200, and your contractor should pull it as part of the job. The installer must be TSSA-licensed for gas work. No permit and no licence are both walk-away signals.
How do I pick an HVAC contractor in London?
Get 2–3 written quotes that itemize equipment (brand, model, AFUE), venting changes, permits, and haul-away — a single-number quote hides the corners being cut. Confirm TSSA certification and ask about manufacturer + labour warranty in writing. Use the quote form below and we'll connect you with qualified local pros.