What AFUE rating should I look for in a furnace?

For most Ottawa homeowners, you should look for a furnace with an AFUE (Annual Fuel Utilization Efficiency) rating of 96% or higher. This is considered "high-efficiency" and represents the best value for our climate over the long term.

Understanding AFUE ratings is straightforward: the number tells you what percentage of fuel is converted to heat. A 96% AFUE furnace converts 96 cents of every dollar of gas into usable heat, while only 4 cents escapes as exhaust. By contrast, an older 80% furnace wastes 20% of the fuel you're paying for.

In Ottawa's climate, this efficiency gap matters enormously. We regularly see temperatures drop to -20°C or colder, meaning your furnace runs hard for 5-6 months of the year. The fuel savings from a high-efficiency unit can be $400-$800 per year compared to an older mid-efficiency model, depending on your home's size and insulation. That adds up quickly over a 20-25 year furnace lifespan.

Ottawa-specific considerations worth knowing: High-efficiency furnaces (90%+ AFUE) use a sealed combustion system with PVC exhaust venting rather than a traditional metal flue. This means installation requires running new PVC pipes through an exterior wall, which adds a small amount to installation cost but eliminates the need for a chimney liner. Natural gas is supplied by Enbridge in Ottawa, and current rates make the efficiency upgrade pay off well within 5-7 years for most homes.

There is one scenario where a mid-efficiency furnace (80% AFUE) might make sense: if you're in a rental property, planning to sell soon, or have a very specific venting situation that makes high-efficiency installation impractical. Your technician can advise on this.

On safety: Any new furnace installation in Ontario requires a TSSA permit and must be performed by a licensed gas technician (G2 or G3 certified). This isn't optional — it's the law, and it protects you. Always ensure your installer pulls the proper permits.

For a free estimate on a furnace replacement or upgrade, reach out to Ottawa HVAC Pro — a contractor can assess your home's specific needs and recommend the right unit for your situation.