About Power Conversion
Power conversions are used in electrical engineering, automotive, and HVAC applications.
Watts and horsepower
The watt is one joule per second. A kilowatt is 1,000 W and a megawatt is 1,000,000 W. The horsepower in this converter is mechanical horsepower, 550 foot-pounds-force per second, which is 745.69987 W.
Other horsepowers exist. Metric horsepower (PS or CV), common in European car specifications, is 735.49875 W, about 1.4% less. Electrical motors are rated with 746 W per horsepower, and boiler horsepower is a much larger unit of about 9,810 W.
BTU per hour for heating and cooling
Air conditioners and heaters in North America are rated in BTU per hour. One BTU/h is 0.29307 W, so a 12,000 BTU/h air conditioner, called one ton of refrigeration, delivers about 3.517 kW of cooling. A 5,000 BTU/h window unit is about 1.47 kW.
Worked example and a common mix-up
A 200 hp engine produces 200 × 0.74570 = 149.14 kW. A 100 kW electric motor is 100 ÷ 0.74570 = 134.1 hp.
Power is a rate, while energy is an amount. A kilowatt-hour on an electricity bill is energy: one kilowatt used for one hour. For joules, calories and kWh, use the energy converter.