How to choose the right furnace size

Although many factors can affect the choice of the furnace for a house, below table outlines most common rules while choosing furnace for a home in Mississauga, Ontario and in the rest of the Greater Toronto Area.

Furnace output for a bungalow

Bungalow Area [square feet]* Furnace Output [BTU/hr]
Built after 1980 Built before 1980
up to 1200 sq ft 40,000 BTU/hr 50,000 BTU/hr
1200 to 1500 sq ft 50,000 BTU/hr 55,000 BTU/hr
1500 to 1800 sq ft 55,000 BTU/hr 60,000 BTU/hr
1800 to 2500 sq ft 65,000 BTU/hr 70,000 BTU/hr
2500 to 3500 sq ft 80,000 to 90,000 BTU/hr 90,000 to 100,000 BTU/hr

*Basement area not included

Furnace output for a semi-detached 2-storey home

Semi-detached House [square feet]* Furnace Output [BTU/hr]
Built after year 1980 Built before year 1980
up to 1500 sq ft 40,000 BTU/hr 50,000 BTU/hr
1500 to 1800 sq ft 50,000 BTU/hr 55,000 BTU/hr
1800 to 2200 sq ft 55,000 BTU/hr 60,000 BTU/hr
2200 to 3000 sq ft 60,000 BTU/hr >70,000 BTU/hr

*Basement area not included

Furnace output for a detached 2-storey home

Detached House [square feet]* Furnace Output [BTU/hr]
Built after year 1980 Built before year 1980
up to 1300 sq ft 40,000 BTU/hr 50,000 BTU/hr
1300 to 1700 sq ft 45,000 BTU/hr up to 55,000 BTU/hr
1700 to 2500 sq ft 55,000 BTU/hr up to 65,000 BTU/hr
2500 to 3500 sq ft up to 65,000 BTU/hr up to 80,000 BTU/hr
3500 to 4500 sq ft up to 80,000 BTU/hr up to 100,000 BTU/hr

*Basement area not included