Kilowatt (kW)
Definition: A kilowatt (symbol: kW) is a unit of power in the International System of Units (SI). It is defined as 1,000 watts. One kilowatt is equal to 1,000 joules per second. The kilowatt is commonly used to measure the power of engines, motors, and electrical devices.
History/origin: The watt, and thus the kilowatt, was named after James Watt, a Scottish inventor who made significant improvements to the steam engine in the late 18th century. The kilowatt became a standard unit of power in the 20th century.
Current use: The kilowatt is used globally to measure electrical power, engine power, and energy consumption. It is commonly used in household appliances, electric vehicles, and industrial machinery.
Horsepower (hp)
Definition: Horsepower (symbol: hp) is a unit of power in the imperial and US customary systems. It is defined as the power required to lift 550 pounds one foot in one second, which is equivalent to 745.7 watts or 0.7457 kilowatts. There are several definitions of horsepower, including mechanical horsepower, metric horsepower, and electrical horsepower.
History/origin: The term "horsepower" was coined by James Watt in the late 18th century to compare the output of steam engines to the power of draft horses. The modern mechanical horsepower was standardized in 1959 as exactly 745.7 watts.
Current use: Horsepower is primarily used in the United States and United Kingdom to measure the power of engines in cars, motorcycles, and other vehicles. It is also used in various other applications, including industrial machinery.