From what I understand, it is MUCH higher than 5%
The 5% comes from a european study I saw years ago.
This is what Wikipedia says:
Transmission and distribution losses in the USA were estimated at 6.6% in 1997[10] and 6.5% in 2007.[10] In general, losses are estimated from the discrepancy between energy produced (as reported by power plants) and energy sold to end customers; the difference between what is produced and what is consumed constitute transmission and distribution losses.
So, yes losses are more that 5% but not much higher.
New cogeneration plants can reach 60% effiency, even with a 10% loss in transmission, that leaves the power plant operating at 50% at your door step.
Traditional automobiles are about 10% efficient over all which give a rechargable electric cars two advantages. One, over all effiency from fuel to pavement would be higher and second, that energy can come from cheaper domestic fuels.