They make "digital PSUs" like the Corsair AXi series that can talk to your PC over a comm port.

Some UPSes can show how much power is being drawn by everything connected to it, in this case presumably your computer.

You probably want a UPS anyway if you've got a power guzzling (and thus presumably expensive) machine.

Many server PSUs and motherboards have a SMBus or similar interface for monitoring. Quite rare on consumer parts, sadly.

Knockoff meters are like $10 on Amazon. Not a bad investment.

I have what is probably a close spiritual cousin of one of those, and while it even touts a power factor display, it also loves to show ridiculously high values during idle consumption for anything involving some sort of power electronics (not just for my computer, but for example for my washing machine, too – it shows sensible values while the heating element runs, or when the motor actually turns, but in-between it shows nonsensically high values).

It is a few years old, though, so maybe by now quality standards have improved even for those kinds of cheapo-meters…