DC or not DC

My previous article reminded me of something that has been on my mind in the past.
Electronic devices, ones that do very little mechanical work, generally operate best with DC power supplies. In mobile devices such as phones or notebooks, the input power is used to charge the battery and it is the battery which supplies the actual electronics. But even in a desktop computer there is an internal power supply which changes the input AC power into various DC voltages before passing it on to the different components.
This is obvious with devices which are charged through a transformer (technically a SMPS). The transformer is commonly a little black box on the power plug which makes it impossible to fit in the socket next to any other device (who designs these things?).
While ideally there is as little as 5% loss of energy in per device, it may actually be significantly higher. And each one is wasting power.
Now AC is supplied to homes because this is the most efficient way to transmit electricity over long distances. Devices which draw large amounts of power – such as whitegoods or power tools – also built make use of the full amount available. But smaller devices need to drop power to reduce it to usable levels and this basically wastes the energy as heat.
An alternative, hinted at above, would be to have a single transformer which converted the input supply to some standard DC voltage for use within the home. As car chargers are common amongst the devices in question, a 12V supply would seem to be appropriate.
It would even be fairly easy so set up such a system. All you need is a couple of car batteries, a trickle charger and a bank of sockets to plug in the device chargers. A competent electrician should be able to do it in an afternoon.
I imagine that the best option in most houses would be a single supply point where mobile devices could be charged, but there is no reason why multiple points could not be spread throughout the house. It would mean a secondary wiring job but DC is a lot easier to deal with than AC and the concept of twinned supply already exists with grey water systems.
Another extension to the concept would be to wire in solar panels (which naturally supply DC) so that the secondary system is fully self-contained.