How much for a second furnace in a Toronto duplex?

Installing a second furnace in a Toronto duplex typically costs $4,000-$8,000 for a standard gas unit, though the total project including ductwork modifications can range from $6,000-$15,000 depending on your home's existing infrastructure.

The wide price range reflects several key factors specific to duplex conversions. If you're converting a single-family home into a duplex, you'll likely need extensive ductwork modifications to create separate HVAC zones. A mid-efficiency gas furnace (80-90% AFUE) runs $2,500-$4,500, while a high-efficiency condensing unit (95%+ AFUE) costs $4,000-$6,500. Installation labor adds another $1,500-$2,500, but the real expense often comes from ductwork modifications, which can add $2,000-$6,000 to create proper zoning.

Toronto-specific considerations significantly impact your project scope and cost. If you're creating a legal secondary suite, Toronto Municipal Code Chapter 150.67 requires separate heating systems for each unit. You'll need building permits from the City of Toronto Building Division, and all gas work must be performed by TSSA-certified technicians. The gas line capacity to your property may need upgrading - Enbridge Gas charges $1,500-$3,500 for service upgrades depending on distance from the main. Your electrical panel may also need upgrading to handle the additional furnace, adding $1,500-$3,000 to the project.

Ductwork complexity drives much of the cost variation in Toronto's diverse housing stock. Century homes in neighborhoods like Leslieville or The Annex often have challenging layouts with limited basement height and existing radiator systems. Post-war bungalows in Scarborough typically offer easier ductwork access. If your duplex shares existing ductwork, you'll need complete separation and possibly additional return air systems. Expect 10-15 business days for permit approval and coordinate inspections with both the city and TSSA.

Professional installation is mandatory for gas connections and electrical work in Ontario. Never attempt DIY gas line work - it's illegal and extremely dangerous. The furnace installation requires TSSA permits and inspection, while electrical connections need ESA permits if panel upgrades are required.

Next steps: Get quotes from licensed HVAC contractors who can assess your existing ductwork and gas service capacity. Schedule consultations in late summer or early fall before the busy heating season. Ensure any contractor you hire is TSSA-certified and can handle the permit process. Budget for potential electrical upgrades and allow 4-6 weeks total project timeline including permits and inspections.