Electric transmission (AC) can loose q fair bit - DC even more. I do not fully recall but at uni I seem to recall 60% losses overall.
It is more efficient to transmit high voltage DC than high voltage AC. You do not have the losses associated with Inductive and Capacitive effects. The reason it is not done is because the power stations generate electricity as AC and the equipment required to convert AC to DC and back again would be very expensive and large and not cost effective. In any case it will still have to arrive at your home as AC.
As far as car chargers are concerned, if you want an OLEV grant to install a charging point there are 3 sizes. 3.7.kw or 15.5 amps, 7kw or 29 amps both single phase and requiring separate wiring to the consumer unit and 22kw which would require a 3 phase supply.
