[throw0101a]

> Low voltage DC (like 12V) requires MUCH thicker cables for the same power, which means a lot more copper (and copper mining). Typical line voltage can be very lightweight.

-48V DC has been a thing with telco equipment for decades: it's what a landline telephone uses for signalling.

* https://www.servertech.com/blog/48vdc-power-and-the-backbone...

If we'd use anything DC, it would probably be that.

[MisterTea]

DC is used where you want direct battery backup, meaning the battery bank voltage is directly supplied to the equipment. This makes the system more reliable as there are no power supplies or inverters to fail. The system can then be composed of simple fuses, breakers, switches and relays to control power flow.

You can even design the system so that the batteries are in parallel with the power supply and load making the system uninterruptible by default.

A lesser known standard is 110V DC used in electrical substations and switchgear. They cover a lot of ground and cable runs can be hundreds of meters so the higher voltage allows longer distances with minimal line loss.

[JKCalhoun]

12V has been standard in auto/marine for quite some time. There are plenty of consumer items that already run on 12V.

Power hogs like refrigerators, window-AC units would no doubt still run on 110/220.

But I already have mixed voltage AC in my home: otherwise 110V but purpose-placed 220V for electric stove/oven (in kitchen) and electric clothes dryer (in garage).

In my perfect future only those high-current outlets would remain — the rest of the house would have 12V plugs and lighting.

[throw0101a]

There is more and more 24V in marine systems to deal with higher loads in recent years. Your 28' (8m) day sailor may not need much more than a starter battery, but once you're at 40' (12m) and above things start changing. E-motors in the marine world generally use 48V (AFAICT).

48V is also being looked at in the auto world as well, at least for "low voltage" stuff:

* https://www.automotiveworld.com/articles/48-volt-likely-to-b...

The IEEE's 802.3bu PoDL can handle sending 12, 24, and 48V, and automotive is one of its deployment spaces:†

* https://blog.siemon.com/standards/ieee-std-802-3bu-2016-powe...

* https://en.wikipedia.org/wiki/Power_over_Ethernet#Standards_...

† 10BASE-T1, 100BASE-T1, 2.5GBASE-T1, 5GBASE-T1, and 10GBASE-T1; .3cz task force is working on 25/50/100 Gb/s.