One mismanufactured cable away from a fire I imagine. There’s a review on Amazon by a (at least at the time) Google of a specific USB-C cable that would burn out the USB-C port on MacBooks because the cable wasn’t manufactured well. In fact, that guy has many many reviews on Amazon of the various defects in various cables (he stopped once that cable burned out his port).

> It's totally possible to deliver 3kw in the form factor of USBC safely

Wouldnt that take like 400V? Not sure how safe that would be.

Did some napkin math for fun. There are 12 contacts spaced within 6mm inside a USB-C cable, on each side. Assuming each contact is 0.25mm wide with a 0.25mm gap between each, it would only take somewhere around 1000V to simply arc through the air between contacts. And anything over 5 amps is going to start causing resistive heating simply due to how small and thin the wires and contacts are. So maybe, if you built it and tuned it really well, you could push up to around 5kW through a USB-C, with it being on the brink of shorting itself out and/or melting itself.

And 10,000 volts build up on your body when you rub a balloon on your head...

With high voltages, it's all down to how many joules you allow to be dissipated in a human. Ie. Current*voltage*time. Specifically, anything over about 0.01 Joules is dangerous. To use high voltages in a consumer product you need to limit either the current or the time, and you need to do it in a way that is very robust to being chewed on by a baby in a bath. And it needs to be robust to that even when built by a corner-cutting factory.

One approach to that is to have either end of the link 'test' the other end - ie. Simulate a human touching the wire. If power isn't turned off fast enough to be in spec, then the remote end or cable isn't working correctly and shouldnt be used.

Wattage is a product of voltage and amperage, so the question would be what the voltage supply is (either 100~120V or 200~240V depending on region) and how much amperage the cable and connections can handle.

To supply 3000W with a 110V supply would require around 28A, which will trip any 10A or 15A breaker commonly found on most house lines going to electrical outlets, but it's well within the realm of something that could be supplied by a circuit equipped with a 30A or higher breaker and qualified wiring.

Of course at 30A or higher, we're talking about things that connect via those bulky connectors you would find on dryers and other high load electronics. Bulky for your safety, mind you.

> To supply 3000W with a 110V supply would require around 28A, which will trip any 10A or 15A breaker commonly found on most house lines going to electrical outlets

The utter, utter majority of the world runs on something around ~230V [1], except America and Japan.

[1] https://en.wikipedia.org/wiki/Mains_electricity_by_country#/...

The US (and CA) runs on 240V as well, it's just split in half for smaller appliances. See requisite Technology Connections video:

* https://www.youtube.com/watch?v=jMmUoZh3Hq4

My stove and clothes dryer are certainly not 120V.

In the same way that 240V countries run on 400V as well then?

Sort of. Outside of industrial or businesses, my understanding is that it is rare to see multi-phase power (400V) used in power applications. You may get 3 phases into your house, but the phases are used separately (each at 240V) for most things in residential.

Stoves are pretty much always at three phases unless it is something like a small summer-house

Washing machines too I've heard.

48V is the max dry “skin” safe voltage that won’t cause a shock.

No, it's not. USB-C doesn't have anywhere near the appropriate amount of creepage/clearance allowance for something high voltage enough to handle 3kW. The only way to handle 3kW is a cable is to completely change the port, at which point it's no longer USB-C.