Cooling Capacity and Units of Measurement: kW, BTU, Ton, and Kcal/h

One of the first challenges anyone working with cooling systems encounters is the confusion created by different units of measurement. You’ll see BTU/h in one catalog, kW in another, and “tons” in yet another. So what do these units mean and how are they related? In this article, we’ll examine cooling capacity units in detail and learn practical conversion methods.

What is Cooling Capacity?

Cooling capacity represents the amount of heat a cooling system can remove from a space in a given time period (usually one hour). In other words, it shows how much “cooling power” the system has. This capacity is expressed in different units in different countries and industries.

Basic Cooling Capacity Units

1. kW (Kilowatt)

Kilowatt is 1000 times the watt, which is the power unit in the International System of Units (SI). It’s the most commonly used and easily understood unit in cooling.

• 1 kW = 1000 Watts
• Standard unit in Europe and many countries
• Used for both cooling capacity and electrical consumption

2. BTU/h (British Thermal Unit per Hour)

BTU is the British thermal unit and is widely used in the United States. One BTU is the amount of heat required to raise the temperature of 1 pound (approximately 0.45 kg) of water by 1°F.

• 1 BTU/h ≈ 0.293 Watts
• Common in the US and UK
• Especially preferred for air conditioning systems

3. Ton (Refrigeration Ton)

Refrigeration ton is derived from the cooling capacity required to freeze 1 ton (2000 pounds ≈ 907 kg) of water at 32°F (0°C) into ice in 24 hours.

• 1 Ton = 12,000 BTU/h = 3.517 kW
• Especially used in large commercial and industrial systems
• Very common in the US, less used in Europe

4. kcal/h (Kilocalorie/Hour)

Kilocalorie is the amount of heat required to raise the temperature of 1 kg of water by 1°C. It’s still used in some countries and older systems.

• 1 kcal/h = 1.163 Watts
• 1 kW = 860 kcal/h
• Especially seen in old catalogs and some European countries

Unit Conversion Table

Unit	kW	BTU/h	Ton	kcal/h
1 kW	1	3,412	0.284	860
1 BTU/h	0.000293	1	0.0000833	0.252
1 Ton	3.517	12,000	1	3,024
1 kcal/h	0.001163	3.968	0.00033	1

Practical Conversion Formulas

Most Used Conversions

1. kW → BTU/h: kW × 3,412 = BTU/h
2. BTU/h → kW: BTU/h ÷ 3,412 = kW
3. Ton → kW: Ton × 3.517 = kW
4. kW → Ton: kW ÷ 3.517 = Ton
5. kW → kcal/h: kW × 860 = kcal/h
6. kcal/h → kW: kcal/h ÷ 860 = kW

Real World Examples

Example 1: Air Conditioner Selection

An office requires an air conditioner with 36,000 BTU/h capacity. What is this in kW?

Solution: 36,000 ÷ 3,412 = 10.55 kW

Example 2: Chiller Capacity

An industrial facility needs a 100-ton chiller. What is the cooling capacity in kW?

Solution: 100 × 3.517 = 351.7 kW

Example 3: Old Catalog Conversion

You see a cooling unit with 50,000 kcal/h capacity in an old catalog. What is this in modern units?

Solution:

• In kW: 50,000 ÷ 860 = 58.14 kW
• In Tons: 58.14 ÷ 3.517 = 16.53 Tons

Which Unit is Used Where?

• United States: BTU/h and Tons (standard)
• European Union: kW (standard)
• United Kingdom: Mix of metric (kW) and imperial (BTU/h)
• Canada: Both systems are used
• Japan: kW and kcal/h
• Middle East: BTU/h and Tons (American influence)
• Australia: kW (metric system)
• India: Mix of kW and Tons

Considerations for Unit Selection

1. Project Specifications: Use whatever unit is requested
2. Customer Familiarity: Prefer the unit the customer is familiar with
3. Equipment Catalogs: Convert from manufacturer’s units if needed
4. Energy Calculations: Using kW makes electrical consumption comparison easier

Quick Tips

1. Quick Estimation: 1 Ton ≈ 3.5 kW (for rough calculations)
2. BTU → kW: Divide BTU value by 3 for approximate kW
3. Mobile Apps: Use conversion apps for accuracy
4. Reference Card: Keep commonly used conversions handy

Common Pitfalls to Avoid

1. Confusing Power Units: Don’t mix cooling capacity (kW cooling) with electrical consumption (kW electrical)
2. COP Factor: Remember that a 10 kW cooling capacity unit might only consume 3 kW of electricity (COP = 3.3)
3. Regional Variations: Be aware that “ton” can mean different things in different contexts
4. Rounding Errors: Use sufficient decimal places for critical calculations

Industry-Specific Preferences

Data Centers

• Typically use kW for both cooling capacity and IT load
• Makes heat load matching straightforward

HVAC Contractors

• US: Primarily BTU/h and Tons
• Europe: Primarily kW
• Mixed markets: Provide both units

Industrial Applications

• Large systems: Often specified in Tons or kW
• Process cooling: Usually kW for integration with other metrics

Conclusion

Understanding and converting cooling capacity units correctly is critical for both proper equipment selection and effective customer communication. With the conversion formulas and practical knowledge you’ve learned in this article, you can easily compare capacities expressed in different units and select the appropriate system for your needs.

Remember: Unit conversion alone is not sufficient for cooling capacity calculations. Factors such as ambient conditions, insulation quality, and intended use must also be considered. For professional projects, always perform detailed heat load calculations.

The cooling industry is gradually moving towards standardization with SI units (kW), but regional preferences remain strong. Being fluent in all common units will serve you well in this global industry.