Source : Webster's Revised Unabridged Dictionary (1913)

Kilowatt hour \Kil"o*watt` hour\ (Elec.)
   A unit of work or energy equal to that done by one kilowatt
   acting for one hour; -- approx. = 1.34 horse-power hour.

Source : WordNet®

kilowatt hour
     n : a unit of energy equal to the work done by a power of 1000
         watts operating for one hour [syn: {kW-hr}, {Board of
         Trade unit}, {B.T.U.}]