[ctdonath2]

The biggest efficiency problem for electricity is transport: about half the power is lost just running it thru long transmission lines.

[Ben Ficklin]

There is some loss to transmission and distribution but your number is grossly exaggerated.

It depends on volts, watts, and distance or AC vs DC and the US is behind China and Europe on DC.

Using Wiki as a source, it was 6.5 percent in 2007. Nation wide.