Ratings & sizing
BTU
British Thermal Unit — the energy needed to raise 1 lb of water by 1°F. The unit HVAC sizing is measured in.
Furnaces and ACs are rated in BTU per hour. A 60,000 BTU/hr furnace can deliver 60,000 BTUs of heat every hour at full burn. Sizing matches BTUs to your home's heat loss/gain.
For a typical 1,500 sq ft Mississauga home with average insulation, expect:
- Furnace: 60,000–80,000 BTU/hr
- AC: 24,000–36,000 BTU/hr (= 2.0–3.0 tons; 12,000 BTU = 1 ton of cooling)
These are starting points only — proper sizing uses Manual J calculations factoring insulation, window area, exposure, infiltration, and internal gains. Sizing by square foot alone is how you end up with an oversized system that short-cycles.
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