The BTU (British Thermal Unit) is a unit of thermal energy measurement originating from the British imperial system, still widely used in the refrigeration and HVAC industry, especially in the Americas.
Technical Definition
1 BTU represents the amount of energy needed to raise the temperature of 1 pound (453.6 g) of water by 1 degree Fahrenheit (0.556°C) at sea level.
Important Conversions
| Unit | Equivalence |
|---|---|
| 1 BTU | 0.252 kcal |
| 1 BTU | 1,055 Joules |
| 1 BTU/h | 0.293 W |
| 12,000 BTU/h | 1 TR |
| 1 kW | 3,412 BTU/h |
BTU/h in Refrigeration
In refrigeration systems, BTU/h (BTU per hour) is used to indicate heat removal capacity:
- Residential air conditioning: 7,000 to 24,000 BTU/h
- Commercial air conditioning: 24,000 to 60,000 BTU/h
- Compact chillers: 36,000 to 300,000 BTU/h (3 to 25 TR)
- Industrial chillers: 300,000+ BTU/h (25+ TR)
Why do we still use BTU?
Despite the International System (SI) using Watts and Joules, BTU remains popular because:
- Industrial tradition: American equipment dominated the market for decades
- Ease of comparison: BTU values are more "round" for common equipment
- Technical documentation: Catalogs and standards still reference BTU
- Consumer market: Consumers are accustomed to the unit