Convert a known power rating between electrical, mechanical and heating units while keeping the definition of each unit visible.
Compare ratings on the same basis
Enter the power and select the source and destination units. Use mechanical horsepower for the conventional 550 foot-pounds-force per second definition, metric horsepower for PS, and electrical horsepower for the explicitly defined 746-watt unit. These differ slightly; a rounded “hp” label alone is not enough to choose between them.
Power is a rate of energy transfer
One watt is one joule per second. Kilowatts describe power, while kilowatt-hours describe energy over a duration. A 2 kW load running steadily for three hours uses 6 kWh. This converter changes the power unit only; the Electricity Calculator can estimate energy use and cost.
Heating, cooling, and input versus output
Btu per hour uses the International Table Btu. A US refrigeration ton is 12,000 Btu per hour of cooling capacity. Converting that capacity into watts does not give the electrical input needed to operate an air conditioner; efficiency connects input to output.
Volt-amperes measure apparent AC power. They are not offered here as though they always equal watts. Use the power factor and voltage in an electrical power calculation to determine real watts. Motor input watts and shaft-output watts also differ by efficiency.
Formula
1 W = 1 J/s
1 mechanical hp = 745.6998715822702 W
1 metric hp (PS) = 735.49875 W
1 refrigeration ton = 12,000 Btu (IT)/h
Examples
A mechanical power rating
100 mechanical hp is approximately 74.56998716 kW. The same number of metric horsepower is 73.549875 kW.
Cooling capacity
12,000 Btu (IT)/h is approximately 3,516.852842 W of cooling capacity, not the appliance electrical demand.
Precision and definitions
Calculations retain unrounded values internally. Displayed digits do not increase the accuracy of measurements. NIST unit definitions provide the conversion reference.