Which modern PC draws 30W when off? When mine is off, the electricity calculator states 0W (the draw is less than it can register).

Even for sleep mode that would be huge. 30W is about the normal modern PC idle (on, but not doing anything) consumption, not any sleep / standby / off state consumption.

My ASRock B450 Pro4 draws about 3W from the wall if WOL is enabled, which in ASRock's firmware seems to keep all PCI devices (and attached USB devices) powered. 30W seems impossible though, anything not specifically designed to be fanless will almost certainly need to turn on the fan at that power usage (and even fanless might have difficulty dissipating a constant 30W).

Monitors can dissipate a huge amount of power without a fan. The OP blames mostly them, and their stand-by power consumption usually isn't even available to a buyer.

Surely the display panel itself is switched off when on standby, though? Is this a case of not including a separate standby power supply circuit, so that it's the "main" one inside there running at a fraction of its capacity, where it is least efficient?

The specific case I'm thinking of was an Advantech AIMB-274 with a Mini-Box PSU (I don't remember which one). I was evaluating this setup for inclusion in a battery powered mobile robot; in particular we needed to decide whether the computer could be hooked up to the battery full time or if there needed to be a relay in between them in order to preserve the battery when the robot was "off". The answer turned out to be that we very much needed to disconnect the computer.

Admittedly this is not a consumer PC or a "modern" gold/bronze-designated power supply, but I still thought it was pretty significant.

Mine is <100W now. Including a big monitor.

30W with high end CPU and graphic card in desktop and tons of plugged pheripals and big screen? They have good power management these days but not that good.

Plus many people use electronics build 5-10 years ago which are generally bigger offenders.

It doesn't matter if it is a computer with multiple GPUs for cryptomining. If it's 'off', PCI should be off, etc.

i worked for a electricity meter maker and measured consumption for things in my house and have now meters on most sockets and so on. 500w idle is huge.

How much is the draw of all those ammeters? i.e. the "burden". I'm having trouble finding what that would be for a typical household plug ammeter without avoiding all the "power meters are great" spam sites. I assume it is very small.

I'm using Shelly EM at the entry (for the entire phase), relays with PM at some sockets with interesting devices and shelly plugs at some sockets that need to be easily serviceable (think behind kitchen cabinets, for the built-ins).

The consumption of each of them is below 1W.

Nobody is missing 50w any more because that goes on their BOM as a bigger power brick. I can see this stuff where someone missed an incandescent or hasn't replaced a device in 10 years but really stuff has moved on and cost optimisation is relentless.

i had access to industrial power meters designed to 120A 400V so that is what i used, but the typical household here would not go over 4-7 kw and you can buy cheap digital meters from AliExpress with display and so on they can measure up to 4kw i believe.

Yes it's huge, but not out of the question for some people who go all in on some things in their house.

For example, in my place right now:

  - Unifi rack (some switches, cameras, other PoE stuff) - 335W
  - Servers (home automation, NAS, etc) - 426W

That's all the time, Unifi actually goes up at night when the IR LEDs come on in the cameras.

That's still insane. I have a Hue bridge and server at home that together draw less than 50W. Network equipment is also in the range of max 10W per device.

That's not "idle" use... somebody wasted good money on those labour-saving devices. And they'll write a blog post about it too once they get around to fixing them!

(I write this lovingly yet seriously as absolutely a victim of this exact same dynamic, sitting next to a pile of expensive fans I'm going to use to reduce the noise from my rack... any day now...).