It's a fact that literally everything in a modern home that doesn't use a heating filament, or a compressor or a motor, runs on either 5 or 12 volts DC.
I understand why we have high voltage transmission and distribution, and I understand why our last mile is 600/220/110 etc but I don't understand why we're not just supplying modern homes with site wide 5 and 12 volt via Class 2 wiring, and why manufacturers aren't offering the option to just provide that kind of switch on products that have their own internal power supplies. So much of what we use right now is also dependent upon even more wasteful "wall wart" outboard supplies which are "always on" even when the product isn't.
And much of that is due to the fact that it is cheaper to design products which are actually on "STANDBY" instead of "OFF".
A few modern homes have "USB" built into every outlet.
I think we need to take the next step and just supply 5 VDC and 12 VDC at every outlet, make the outlets "smart" and switchable and do away with the wall warts.
We would also be able to make lighting much simpler then as well, and solar could bypass a lot of the inverter stages.
Computer internals have this figured out already. High powered graphics cards demand two (4 pin, six pin and 8-pin) 12 volt supply plugs from the motherboard, so for high current 12 volt devices, just do the same thing externally and do USB for all the 5VDC products.(Computer 12 volt connector) (These are 4-pin but are also available in 6-pin and 8-pin)
We'll still need the 120 volt AC for all our power tools, vacuum cleaners, blenders, toaster ovens, microwaves and the like but so much of what we use simply isn't running off 120 volts AC and never even did in the old days. It's just that it had a transformer, rectifiers and filter capacitors internally.
In the early 80's I still had a great big 1974 Dodge Tradesman 300 van and I stuck a Pioneer SX-838 stereo receiver in the back along with a cassette deck and speakers.
I bypassed the internal power supply and ran it direct off 12 volts and that worked for almost five years. All I had to do was go directly to the great big red and black wires on the main board and voila.