How many BTU for 300 sq ft?
Updated October 24, 2026
To heat 300 sq ft (28 m²) you need between 4,500 and 6,600 BTU/h depending on your city and insulation. Here is the calculation city by city, using the CSA F280 method.
Assumption: a 300 sq ft main-floor room, two exterior walls, 2 windows, 8 ft ceiling.
Heating load by city and house age
| City | After 2010 | 1990 to 2010 | 1970 to 1990 | Before 1970 | Cooling* |
|---|---|---|---|---|---|
| Vancouver (-7 °C) | 4,500 | 4,500 | 4,500 | 4,500 | 2,200 |
| Toronto (-18 °C) | 4,500 | 4,500 | 4,500 | 4,900 | 2,500 |
| Halifax (-16 °C) | 4,500 | 4,500 | 4,500 | 4,700 | 2,100 |
| Montreal (-23 °C) | 4,500 | 4,500 | 4,500 | 5,500 | 2,300 |
| Quebec City (-26 °C) | 4,500 | 4,500 | 4,500 | 5,900 | 2,200 |
| Winnipeg (-31 °C) | 4,500 | 4,500 | 4,700 | 6,500 | 2,300 |
| Edmonton (-32 °C) | 4,500 | 4,500 | 4,800 | 6,600 | 2,100 |
* Cooling for a 1990–2010 house, at the city’s summer design temperature.
Which Kanartic system for 300 sq ft?
Newer house in Toronto
ZERO 9,000 wall unitfrom $2,199 · DIY
Covers 100% of the heating load at -18 °C
The 9,000 BTU wall unit is not eligible for any rebate.
See on kanartic.ca1990–2010 house in Montreal
ZERO 9,000 wall unitfrom $2,199 · DIY
Covers 100% of the heating load at -23 °C
The 9,000 BTU wall unit is not eligible for any rebate.
See on kanartic.caPre-1970 house in Edmonton
ZERO 9,000 wall unitfrom $2,199 · DIY
Covers 100% of the heating load at -32 °C
The 9,000 BTU wall unit is not eligible for any rebate.
See on kanartic.caWhat about 25 BTU per square foot?
The rule of thumb would give 7,500 BTU/h for 300 sq ft. The component calculation gives 4,500 to 6,600 BTU/h: depending on the house and climate, the rule is off by +14% to +67%.
Frequently asked questions
Is a 12,000 BTU heat pump enough for 300 sq ft?
In Montreal, for a 1990–2010 house, a 12,000 BTU unit covers 100% of the load at -23 °C; for a pre-1970 house, 100%. So it is enough for a newer or renovated house.
How many BTU to cool 300 sq ft?
Between 2,100 and 2,500 BTU/h for a 1990–2010 house, depending on the city. In Canada, heating sets heat pump size, not cooling.
Wall unit or multi-zone for 300 sq ft?
A single wall unit is enough for a room this size.
Other floor areas
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