does a power supply use all of the watts all of the time

[lamontbond]

i was wondering if a 500 watt power supply uses 500 watts all of the time or does it just give enough power for each of the components up until 500 watts?

 

[Beliar]

It can support up to 500W, it gives as much power as needed.

 

[Zepper]

Most computer PSUs are switching designs that adjust output based on load and draw AC power accordingly. However the effiency (Watts out/Watts in x 100 = efficiency (in %) gets better as the total ouput rises above half - so you don't want to run too big of a PSU.
. My PSU is a 350 Watter and it seldom draws more than 200W AC. There are a couple of meters out there that can show your AC usage (and other factors) if you are really curious: one is the P3 "Kill A Watt" (best price is on eBay), the other is the Seasonic Power Angel (newegg et al. carries them) - both are actually the same design in different packages.
.bh.

 

[Jeff7]

Originally posted by: Zepper
Most computer PSUs are switching designs that adjust output based on load and draw AC power accordingly. However the effiency (Watts out/Watts in x 100 = efficiency (in %) gets better as the total ouput rises above half - so you don't want to run too big of a PSU.
. My PSU is a 350 Watter and it seldom draws more than 200W AC. There are a couple of meters out there that can show your AC usage (and other factors) if you are really curious: one is the P3 "Kill A Watt" (best price is on eBay), the other is the Seasonic Power Angel (newegg et al. carries them) - both are actually the same design in different packages.
.bh.

I got the Kill A Watt - nifty little thing. Useful for finding out just how much power a device uses when it's "turned off" - my Logitech z-640's for example - the subwoofer emits a very quiet hum, and it uses about 5 watts even when it's "off." Now granted, things like TV's and VCR's that you want to turn on with a remote, they need to use a little bit of power for that. But that should be reduced too with a very small passive circuit, maybe with something simple like a relay. But speakers? Why should they need any power when not turned on?
Well, there I went on a rant about power conservation, or the lack thereof. Sloppy design wastes too much power....

Only complaint about the Kill A Watt - it doesn't go low enough. I'd love to measure some really low-power plug-in components, but that'd probably need a more precision-built product, or one calibrated differently.
It's simple to use otherwise - plug it in, then plug the device in.
All I need is another Kill A Watt now to see how much power each Kill A Watt uses by itself.

 

[Zepper]

Kill A Watt uses 10 Watts max. according to its manual, but that sounds mighty high to me. Maybe that's mostly the shunt resistance it uses to measure Amps. See my review of the Kill A Watt here: http://www.techimo.com/reviews/ in the Power Supply section.

.bh.