DrFixIt Defines Power. The Definition of Work and PowerThe Definitions of Work and Power in the English and Metric Systems. DrFixIt Defines the Term Power and provides practical examples as well as rules of thumb. 

Work is done by applying a constant force to an object, thus moving it. If a Pound of force is needed to move an object one Foot, the work done is one FootPound of work. Similarly, in the Metric System, A NewtonMeter (Also called a Joule) of work is performed by applying a constant force of one newton which moves a body a distance of one meter.
Time is not involved in the definition of work. The amount of work performed is the same, say, in lifting a weight a specific vertical height regardless if the action of the lifting takes a minute or an hour. However, the amount of time needed to perform that lifting work leads to the concept of POWER.
The measurement of power, then, involves a description of the work as a ratio to the time it took to perform. This is a scientific definition of what most people understand instinctively: One needs more "power" to go faster or to do more in the same amount of time.
In the British system, the unit of power is, simply, the FootPound/Second (Work divided by Time). In the Metric System, a NewtonMeter/Second (Work divided by Time) is also called Joule/Second or most familiarly, a Watt.
Both the FootPound/Second and the Watt are quite small units of power. Larger units of work are more commonly used. In the British system, a Horsepower is defined as 33000 FootPounds of work in performed in one Minute (the same as 550 FootPounds per Second) . In the Metric System, a Kilowatt is simply 1000 watts.
By just converting Pounds to Newtons (Force)and Feet To Meters(Distance) it can be easily calculated that:
A good rule of thumb is that 1 Horsepower is about 3/4 of a Kilowatt.
So What? It turns out to be handy when one can apply a form of Ohm's Law:
As an example, we can now see that a Horsepower motor plugged into a 120 Volt circuit would (ideally) draw:
In reality, the motor will draw a little more current than 6.22 Amps because of heat loss and other natural inefficiencies. Usually motors are within the 75% to 90 % efficiency range so, in the shop, the above motor would probably really pull about 6.22 amps / .75 (efficiency estimate) = 8.29 Amps.
Nameplate missing on a motor? Need to know what size it is? Measure Amps, Volts and do the math!
KiloWattHour = 1000 Watts x 3600 Seconds
=1000(Newton Meter / second) x 3600 seconds
=1000 x 3600 Newton Meter
= 3,600,000 Newton Meters (Joules)
The best name for an electric utility should be a "Joule Company" or a "Newton Meter Company" or a "Foot Pound Company"
Foot Pounds! Get your fresh Foot Pounds here! Foot Pounds!