Electric Power
Key Questions

First of all, kilowatthour od kilowatt hour has many symbols: kW·h, kW h or kWh. It is a unit of energy equal to 1,000 watthours, or 3.6 megajoules.
Very simple:
If the energy is being transmitted or used at a constant power over a period of time, the total energy in kilowatthours is the product of the power in kilowatts and the time in hours.It is commonly used as a billing unit for energy delivered to consumers by electric utilities.

We know that electric power dissipated as a result of Joule's effect is given by,
#P = I^2Rt# , thus in order to minimize the power loss, the current is supplied under very high voltage and as a consequence of law of conservation of energy, the current is reduced and substantially heat loss is also reduced.