Watts and Horsepower

• Horsepower (hp) represents a unit of power, or, more specifically, the rate of work. The watt (W) also represents a unit of power, and these units can be converted directly because 1 hp = 745.7 W.
  
  

Amperes

• Amperes represent the rate of flow of charge in an electric circuit, technically expressed as Coulombs per second and referred to as "current." Multiplying the amperes by the voltage of the circuit gives the power of the device. Mathematically, this is expressed as P = IV, were P is power (in watts), I is current (in amperes) and V is potential (in volts). Determining the power of an electrical device therefore requires knowledge of a circuit's voltage.
  
  

Converting hp to Amperes

• To convert horsepower to amperes first requires conversion to units of watts. The conversion factor is 1 hp = 745.7 watts. Thus, a 3-hp electric motor would operate at 3 hp * 745.7 W/hp = 2237 W. Converting this value to amperes requires knowledge of the voltage on which the device operates. If the motor is operating on 120-volt household voltage, then this converts to 2237 W / 120V = 18.6 A.