Horsepower (hp)
Horsepower, symbol hp, is a non-SI unit of power introduced in the late 18th century by James Watt. He developed the term to market his steam engines by relating their work to that done by draft horses. One horsepower was standardized as 550 foot-pounds per second, or about 745.7 watts in mechanical terms. Despite not being metric, horsepower remains widely used in the automotive, aviation, and machinery industries, particularly in the United States and the United Kingdom. Its continued popularity is due to tradition and the practicality of relating to horsepower over abstract units, such as watts. Bridging from non-metric to metric units, the megawatt further illustrates the diversity and scope of power measurement in modern contexts.
Megawatt (MW)
The megawatt, symbol MW, equals 1,000,000 watts or 1,000 kilowatts. It is a crucial unit in power generation and large-scale energy utilization. The term first appeared in the early 20th century as national grids and industrial-scale electricity production developed. The megawatt became a key measure for the output of power plants, wind farms, and large infrastructure projects. For example, a modern wind turbine may produce between 2 and 5 MW, while large nuclear plants can generate more than 1,000 MW. The megawatt links laboratory science with industrial application, making it vital in global energy planning and addressing climate challenges. Finally, for understanding heating and cooling, a different unit—BTU per hour—is often used, especially in North America.