Definitions:
Horsepower (abbrev. hp): A unit of power. One horsepower equals 550 foot-pounds per second or 746 watts.
Kilowatt (abbrev. kW; pl. Kilowatts): A unit of power equal to 1,000 watts.
Power: 1. The rate at which energy is transferred or converted per unit of time. 2. The rate in which work is done. Units of power include Horsepower, Kilowatt, Megawatt, and Watt.
Watt (abbrev. W; pl. Watts): A unit of power. One watt equals the production or use of one joule of energy per second.