Power Converter

What power measures

Power shows how fast work is done, or how fast energy is used or transferred. The SI unit is the watt (W), equal to one joule per second.

Main units and where they are used

• Watt (W) – bulbs and chargers; kilowatt (kW) – appliances, engines and electric vehicle charging.
• Megawatt (MW) – power plants and industry.
• Horsepower (hp, 745.7 W) and metric horsepower (PS, 735.5 W) – car engines.
• BTU per hour (about 0.293 W) – air conditioners in the USA.

Common pitfalls

The most frequent mistake is mixing power with energy: 1 kW is power, while 1 kWh is an amount of energy. A second is failing to tell horsepower types apart: mechanical and metric differ by about 1.4%, and older documents may use other definitions. A third is assuming higher power means a device uses more: that depends on how long it runs. In car registration papers power is given in kW.