[bluGill]

You would need larger wires to account for the losses at a house scale. Since nothing runs are 48 volts you still have the bad power supply in every LED bulb.

[dreamcompiler]

12 gauge wire would work fine for 48v lighting loads; probably 14 gauge too for many of them. Small DC constant-current sources are commodity items now and they're very efficient.

[bluGill]

12 gauge is more expensive, and harder to work with.

[dreamcompiler]

And it's already in a lot of houses, which was my point.