dumb question about power usage

You have to investigate transformer and rectifier theory. The primary coil (load) is connected directly to the AC (source) input. As current flows through the primary coil (and in some cases a secondary and tertiary coil), voltage is dropped across the loads. This AC voltage is reduced to about 12 volts AC, and then the rectifier (probably bridged) circuits convert the AC to pulsed DC, which is then smoothed out to pure CD (filtered) by the capacitors.

As more and more components use the filtered DC, more current is drawn from the source, and, therefore, more wattage is available.

Without precise winding values, diode effeciency, capacitor values (time constants), and specific DC voltages in addition to the basic 12 VDC, the answer is probably. Maybe a little less at idle.

This would not mean you constantly consume that amount. It only means it's the maximum available to your PC. To determine what is being consumed at idle, you'd need a device between the the outlet and the PS that would measure amperes and voltage and calculate this using the formula P=I x E or power (in watts) equals amperage times voltage. If your system requires a 400 watt PS, it's probable that your maximum usage under heavy load is somewhat less than that and your idle current is considerable lower. The PS won't be 100 % efficient so some power is consumed by it. But to answer your question simply, a 500 watt PS doesn't run at that capacity when a PC is just sitting there idle. Some numbers I've seen suggest that PCs drop back to about 1/3rd or less of the maximum they can consume but your mileage may vary.

I have an AMD X2 4800+ with

2 HDDs
2 CD/DVD Burners
2GBs RAM
Radeo X700 GPU
620 WATT PSU....

At bootup my Kill A Watt shows it goes as high as 150W but at IDLE it draws about 100-110W.

So bottomline ....you'd be a long way from 500W or 620W in my case at idle.

Hope this helps.

VAPCMD

That's LCD monitor, Core 2 Duo processor and NVIDIA 6200 video.

- 158 W doing nothing
- 128 W doing nothing with monitor turned off (so monitor uses 30 W)
- 170 W viewing online TV in window
- 190 W viewing online TV full screen
- 200 W running 1 CPU core 100% (50% overall) [by running a loop in an Excel macro]

This primarily shows the effect of using the CPU. That takes power. That's why needs cooling. A NVIDIA 6200 video card is a very lowly one, that comes without cooling, so it has a rather low power consumption.

The surprise came when I measured the power saving modes.
- 137 W standby with monitor turned black
- 134 W standby with monitor turned off
That means that standby with monitor turned off used MORE power than running with monitor turned off. I never checked this before, I happened to believe Windows when it said it should save power and the motherboard maker to have implemented it. Something wrong here.

Hibernate, however, gave the expected results: 21 W.

Kees