Conversion Factors and Definitions.

 

List of Conversion Factors.
     
1 sq. ft. = .0929 square meters (m2 )
1 sq. yard = .836 m2
1 sq. meter = 10.76 sq. ft.
1 acre = 4047 m2 = 43,560 sq. ft. = 4840 sq. yds.
1 sq. mile = 640 acres
1 hectare = (100m)2 = 2.47 acres

 

Definitions.
 
Energy - the amount of work that a physical system is capable of performing, including mechanical, physical or electrical tasks, or heat transfer between two objects of different temperatures.
Units:

Joule - the amount of energy exerted when a force of one newton is exerted over a distance of one meter. (One newton is the force required to cause a mass of one kilogram to accelerate 1m/sec2)

kWh - the power of x- kW applied for h-hours.
 
Power - the rate at which energy is used, produced or transferred: energy/time.

Units:

Watt - 1 joule per second.

Kilowatt (kW) - 1000 watts = 1.36 horsepower.

Megawatt - 1 Million watts.
 

It is common to confuse energy and power. Note that power can be measured at any moment in time, whereas energy has to be measured during a certain period, e.g. a second or hour or day. For a primer about energy and power, see Danish Wind Industry Association definitions: http://www.windpower.dk/stat/unitsene.htm.