Prototype of RTX 5090 Appears With Four 16-Pin Power Connectors, Capable of Delivering 2,400W

It's the same current but double the voltage

And wiring is typically rated for current limits not voltage (within reason). Some 12 gauge wire doesn't care if you're pushing 12V, 120V, or 240V but is only rated for 20A.
- The easiest way to think about it is that the conductor is rated for the current, and the insulator is rated for the voltage. Now, once you get into the nitty gritty, they're more intertwined than that, but it's close enough for a surface level explanation.

I live in a 50 year old house. All the breakers are 16A, so 220V x 16A = 3.5kW

The electric sauna does three-phase @ 400V. My energy tracker usually peaks around 9.5kW when it's heating.

Most are actually 230V which is even more at standard 16A, 3680W to be precise.
Countries that use 110V have so many weird limitations that we don't even know in Europe. For them, 230V is the "special" outlet for special purposes.
- Actually, in the US the outlets are often wired with 1 leg, while giving 2 legs gets you back to 240v.
  110 is probably better in terms of general safety (which is good because our houses are death traps), but it means when you do need power you need a special circuit.
  We should have both more common, but the plugs are terrible (basically they turn the left prong 90 deg).
  
  when you do need power you need a special circuit.
  We also have a standard socket and a high power socket.
  Expect our normal outlets provide 230V 16A 3.5kW (3kW sustained) and the typical high power outlets outlets provide 400V 30A 11kW or 400V 60A 21kW.
  Which is why typical electric stoves here use 11kW and typical instant water heaters use 21kW.
  Though probably the most noticeable advantage is in electric car charging.
  
  Yeah, in Sweden I charge our plug in hybrid off 240, it's pretty quick and you can use any outlet.
  The giant round connectors are weird BTW, with all the holes, trying to sort that out for faster charging.
  I don't think we should run 100+ volts everywhere, we need to standardize on lvdc in most places (basically usb-c or so) with 100v only in kitchens and places you need it, because it's more dangerous and can cause fires more easily.
  
  That's a common misconception. It's the Amps that cause fires, not the voltage.
  The 5090 uses 600W, at 12V that's 50A, but at 120V that'd only be 5A and at 240V only 2.5A.
  50A melts cables and burns your PC down, 2.5A won't. The only risk of higher voltages is that they can jump across small air gaps much easier.
  
  No it's not, I'm an ee.
  P = I^2R, so power squares against the current, while it's linear to voltage.
  This means current causes more heat dissipation in the wire, which has risks, potentially fire if you really go too far, this is why breakers trip.
  But what really causes fires (again, outside of crazy overcurrent) is Arcing, from basically either bad connections or bad insulation, OR, from an inductive load that gets disconnected, so the current tries to stay constant in the coils, which leads to massive voltage spikes.
  
  The recent technology connections video cited a lot of statistics on this topic, and at least household fires are primarily caused by overcurrent, not by arcing.
  You probably know more than me — I only studied compsci with ee as minor — but from my personal experience, I've seen many cases where overcurrent caused damage, burns or fire, but I can't remember a single case where arcing caused actual damage.
  Even in cheap chinesium powerstrips, the primary cause of fires is overcurrent due to AWG 22 copper clad iron wire, not arcing. (Though the switches usually weld themselves together after a few dozen uses).
  
  Arcing causes more fires, because over current caused all the fires until we tightened standards and dual-mode circuit breakers.
  Now fires are caused by loose connections arcing, and damaged wires arcing to flammable material.
  Breakers are specifically designed for a sustained current, but arcing is dangerous because it tends to cascade, light arcing damages contacts, leading to more arcing in a cycle.
  The real danger of arcing is that it can happen outside of view, and start fires that aren't caught till everything burns down.
  
  110 is probably better in terms of general safety
  Eh, not really. There is no significant difference in safety between 110vac and 230vac. Voltage is not the (most) dangerous part, it's the amps that kill if you're electrocuted.
  
  Amps are voltage over resistance (I = V/R), volts absolutely matter, the human body has a decent resistance and the higher voltage helps burn through that.
  
  There's a reason we talk about lethal current and not lethal voltage...30mA can kill you, even at something ridiculously low as 9V, but 5-10kV will not necessarily kill you, e.g. fences for horses will not kill you if you're electrocuted by them because there's basically no amperage. Voltage is not the determining factor in lethalness.
  
  In most household shocks, you touch a conductor, and you are the resistor to ground. Your resistance is independent of the drive voltage, so if you touch a 110V wire, the current will be half of what you get with a 220V wire. So the voltage determines the current, and thus the lethality.
  There’s lots of other factors that go into the effective resistance like the amount of moisture on your skin, what shoes you’re wearing, and what the floor is made of, etc, but in all cases twice as much voltage will cause twice as much current. You are by far the highest resistance element in the circuit, so your resistance will completely determine the current - most household circuits are capable of supplying 10-15A continuously, so your resistance is the current limiter.
  It’s a bad idea either to go touching live wires either way, but the rule of thumb I heard was was that a 110V shock usually won’t kill you and 220V shock usually will.
  
  It’s a bad idea either to go touching live wires either way, but the rule of thumb I heard was was that a 110V shock usually won’t kill you and 220V shock usually will.
  That's completely incorrect though. I've been shocked by 230VAC at least a dozen times, if not more. And the fuse for the circuit absolutely should not be the limiter, the RCCB should trip WAY before the main fuse.
  
  And the fuse for the circuit absolutely should not be the limiter, the RCCB should trip WAY before the main fuse.
  While that certainly SHOULD be the case, in the US at least while RCCBs (we call them GFCIs) are generally required in wet areas and perhaps for new construction, in most older houses the majority of circuits don’t have any sort of ground fault protection other than the fuse/breaker. In my current house we have them on only two outlets - one in a bathroom and one in the kitchen.
  
  Wild...we don't have them on outlet-basis, it's the entire house that's protected by them, they're installed at the power-inlet to the house so everything is protected by it. And they're mandatory even on old houses.
  
  There is no current without voltage, what you're saying makes no sense.
  Current is voltage over resistance, you get as much current as you have voltage, unless there's an artificial effect limiting voltage, like a voltage regulator or zener diode or just fet.
  When you say 'it's the current', that electric fense has x volts before you touch it, and the fact that it doesn't kill you means either the voltage is too low to produce a decent current in your body, or, there's a voltage regulator/limiter that means when you touch it the voltage drops to some lower level, which I could calculate using the nominal resistance of the human body and the voltage of the fence.
  In a way, the output impedance of whatever is driving the fence determines how much the voltage drops under load.
  I'm speaking about the voltage needed to get the deadly current across the critical areas of your body BTW, which can be handled as a kirchoff circuit I'm sure.
Nominally EU voltage is 230V, and may be 240V. In fact, it can be as high as 230V +10% = 253V. Higher voltage means more power for a given current, so nominally it's 16A x 230V = 3.68kW, but you could have say 16A x 250V = 4.0kW.
If your sauna is 400V then it sounds like you'll be 230V (400V / sqrt(3) = 230). But the voltage can also be 230V -6% = 216V, so 220V is within scope.
But yeah, standard voltages in the EU are either 230V/400V or 240V/415V. They've been harmogenised, but if you look at the numbers you'll see the trick - 230V +10% is roughly the same as 240V +6%. So the range is 230V-6% and 240V+6%.
You've got a 3 phase connection though so you might find you've got different single phase breakers on different phases (eg lights on one phase, sockets on another), with slightly different voltages for each one.

The installation in my home follows my country's regulations as they were ~15 years ago. It's divided into several circuits, the 'general use' outlets one is rated for 25A in total AND at any point, ie you could plug a 5750W appliance in any of those outlets. The lights circuit is the lowest rated at 15A, still letting you 'plug' up to 3450W.