Methodology & sources

Heat demand

For each month we take the city's climate-normal average temperature and assume daily temperatures vary around it (standard deviation 5.5°C). A home needs heat whenever it is colder than 18°C outside; below that, heat loss grows in proportion to the temperature difference. Heat loss per square foot depends on insulation level:

Poor (pre-1970, drafty): 0.16 W/K per sq ft
Average (1970s–1990s): 0.11 W/K per sq ft
Good (2000s, upgraded): 0.08 W/K per sq ft
Excellent (new / high-performance): 0.055 W/K per sq ft

Check: a 2,000 sq ft Toronto home with average insulation comes out at about 67 GJ of heat a year. That is in line with a typical Enbridge customer using 2,400 m³ of gas a year for heating plus hot water.

Heat pump efficiency

Coefficient of performance (COP) falls as it gets colder. Cold-climate model: COP = 2.75 + 0.055 × T(°C), between 1.6 and 4.3, with electric resistance backup below −26°C. Standard model: COP = 2.5 + 0.07 × T, between 1.4 and 4.2, with backup below −15°C. We average across each month's temperature range, so cold snaps count.

Fuel systems

Natural gas furnace 95% (or 80%) efficient; oil furnace 85%; propane furnace 95%; baseboard 100%. Energy content: heating oil 38.68 MJ/L (138,500 BTU/gal), propane 25.3 MJ/L (91,500 BTU/gal), 1 Mcf of gas ≈ 1.055 GJ. The gas fixed monthly charge is added in months that need heat.

Sources

Limits

These are estimates for comparison, not quotes. They exclude water heating, sales tax, time-of-use pricing, equipment, maintenance and rebates. Your home's real heat loss can differ a lot from the insulation presets. Prices last reviewed November 8, 2026.