How to convert power
Power is energy per unit time: 1 watt = 1 joule per second. There are several horsepowers. Mechanical horsepower (745.7 W) is used in the US and UK. Metric horsepower (PS, 735.5 W) is used by many car makers in Europe and India. Electric horsepower (746 W) rates electric motors.
- kW to hp: multiply by 1.34102 (100 kW = 134.1 hp).
- hp to kW: multiply by 0.7457.
- AC tonnage: a 1-ton air conditioner removes 12,000 BTU/h = 3.517 kW of heat. A 1.5-ton AC is about 5.28 kW of cooling. Its electricity use is lower, typically 1.2–1.8 kW depending on its star rating.
Common power conversion factors
| Unit | Equals | Reverse |
|---|---|---|
| 1 horsepower (mechanical) | 0.7456998716 kW | 1 kilowatt = 1.34102209 hp |
| 1 watt | 3.412141633 BTU/h | 1 BTU per hour = 0.2930710702 W |
| 1 ton of refrigeration | 3.516852842 kW | 1 kilowatt = 0.2843451361 TR |
| 1 metric horsepower (PS) | 0.73549875 kW | 1 kilowatt = 1.359621617 PS |
| 1 ton of refrigeration | 12,000 BTU/h | 1 BTU per hour = 0.0000833333 TR |
| 1 horsepower (mechanical) | 745.6998716 W | 1 watt = 0.0013410221 hp |
| 1 megawatt | 1,000 kW | 1 kilowatt = 0.001 MW |
| 1 kilocalorie per hour | 1.162222222 W | 1 watt = 0.8604206503 kcal/h |
Power conversions
Each of these has its own page with the formula, worked examples and a full conversion table:
All power units on this converter
| Unit | Symbol | 1 unit equals | System |
|---|---|---|---|
| Milliwatt | mW | 0.001 W | Metric (SI) |
| Watt | W | 1 W | Metric (SI) |
| Kilowatt | kW | 1,000 W | Metric (SI) |
| Megawatt | MW | 10,00,000 W | Metric (SI) |
| Gigawatt | GW | 1,00,00,00,000 W | Metric (SI) |
| Horsepower (mechanical) | hp | 745.6998716 W | Horsepower |
| Metric horsepower (PS) | PS | 735.49875 W | Horsepower |
| Electric horsepower | hp(E) | 746 W | Horsepower |
| BTU per hour | BTU/h | 0.2930710702 W | Heating & cooling |
| Ton of refrigeration | TR | 3,516.852842 W | Heating & cooling |
| Kilocalorie per hour | kcal/h | 1.162222222 W | Heating & cooling |
| Foot-pound per second | ft·lbf/s | 1.355817948 W | Other |
| Joule per second | J/s | 1 W | Other |
Frequently asked questions
How many kW is 1 hp?
1 mechanical horsepower = 0.7457 kW. 1 metric horsepower (PS) = 0.7355 kW.
What does 1.5 ton AC mean?
It is cooling capacity, not weight: 1.5 tons of refrigeration = 18,000 BTU/h = 5.28 kW of heat removed. The power it draws from the wall is much lower.
What is the difference between hp and PS?
PS (Pferdestärke) is metric horsepower, 735.5 W, about 1.4% less than mechanical hp (745.7 W). Indian car brochures often quote PS or bhp.
How many BTU per hour is 1 kW?
1 kW = 3,412.14 BTU/h.