Quickly convert between BTU/hr (British Thermal Units per hour) and kilowatts—the two most common HVAC power ratings. Whether you're sizing a new system, cross-checking equipment specs, or working with international standards, this free tool eliminates calculation errors.
Converter Tool
Common HVAC Ranges
| Category | BTU/hr | kW |
|---|---|---|
| Window AC (small) | 5,000 | 1.5 |
| Window AC (large) | 12,000 | 3.5 |
| Residential (1-ton) | 12,000 | 3.5 |
| Residential (2-ton) | 24,000 | 7.0 |
| Residential (3-ton) | 36,000 | 10.5 |
| Residential (5-ton) | 60,000 | 17.6 |
| Commercial (small) | 100,000 | 29.3 |
| Commercial (medium) | 150,000 | 43.9 |
| Commercial (large) | 240,000 | 70.3 |
| Industrial (high-capacity) | 500,000 | 146.5 |
How to Use
- Enter a value in either the BTU/hr or kW field.
- See the conversion instantly in the other field.
- Swap fields using the ⇄ button to reverse the input order.
- Reference the table below to see typical system sizes.
BTU vs kW — What's the Difference?
BTU/hr (British Thermal Units per hour) is the imperial unit used in North America to rate heating and cooling capacity. One BTU is the energy needed to raise 1 pound of water by 1°F.
kW (kilowatts) is the metric unit for power, widely used in international standards and modern engineering. It measures energy consumption or output in thousands of watts.
The exact conversion: 1 kW = 3,412.142 BTU/hr. This ratio comes from the definition of a BTU and the watt as a physical unit of power.
Example: 3-Ton AC Unit
Question: A residential 3-ton air conditioning unit is rated at 36,000 BTU/hr. What's that in kilowatts?
Answer: 36,000 BTU/hr ÷ 3,412.142 = 10.547 kW
This is why you might see 3-ton units listed as "10.5 kW" or "10.6 kW" in international documentation.
Frequently Asked Questions
What is the conversion factor between BTU and kW?
1 kW equals exactly 3,412.142 BTU/hr. This is the standard thermal energy conversion used in HVAC and mechanical engineering.
What does BTU/hr mean in air conditioning?
BTU/hr (British Thermal Units per hour) measures the cooling or heating power of an HVAC system. It indicates how much thermal energy the system can remove or add per hour.
How do I know what size AC unit I need?
Cooling capacity is typically 15-20 BTU/hr per square foot of living space. A 3-ton unit (36,000 BTU/hr) cools approximately 1,500-2,000 sq ft. Consult a professional for accurate sizing based on climate, insulation, and local conditions.
Why do contractors use both BTU and kW measurements?
The HVAC industry traditionally uses BTU in North America and kW in international markets and newer engineering specifications. Modern contractors need both for compatibility with different specifications and equipment sources.
What's a "ton" in air conditioning?
One refrigeration ton equals 12,000 BTU/hr or 3.52 kW. It's derived from the cooling power needed to freeze 1 ton of water in 24 hours. Common residential sizes are 1.5–5 tons.