Take a look at the following chart for the total energy usage of the USA in 2008. This is public knowledge and easily accessible.
You will notice that the US burned fuel to create 40 quads worth of electrical energy.
You will also notice (on the far right side of the chart) that under 13 quads (12.68) were actually used. That correlates to wasted electrical energy of 70%. In other words- the power plants must create 1000 kW or energy, but because of inefficiencies in the grid, the transformers, heat, etc. only 300 kW actually get used at YOUR house.
What a waste!
Think of the efficiencies that would be possible if we had thousands (OK, millions) of small Photovoltaic energy systems distributed close to the places where the energy gets used. It would radically decrease the energy loses by transmission (because electrical energy would be produced near where it gets used).
Keep on learning!