I would love to see a Fermi estimate of this, I'm afraid it's outside my bailiwick.

The proposal would be 48VDC (pretty standard for panels) to 120VAC 50Hz, back to 5 and 12 volt at the application, versus sending 12 and 5 volt around a house, call it 10x10 meter perimeter and pessimize the layout (some outlets go all the way around the house).

My strong sense is that the single-step conversion beats the three-step, but losses transmitting low voltage DC are substantial.