How much electricity does a power supply draw?

[LynLabahn]

Guys, I have been thinking about setting up some old computers to crack RC5/OGR/SETI, but I have a concern. My question lingeres on this, does a computer power supply draw its maximum wattage at all times? Say, if you have a 150 Watt power supply, is the draw always gonna be 150 watts? Or is it relative to what he computer uses, like 56.89 watts or whatever it may be. The reason ask is, if you have say 600 Watts of power supplies running 24/7, at 7 cents a killowatt hour, thats gonna cost you 30 dollars a month to power the damn things!Assuming they draw the maximum wattage at all times. Just curious.

Lyn Labahn

 

[Rigoletto]

Of course they don't. Even I know that. If your parts weren't drawing that then the only way to dissipate such current would be as heat. I am pretty damn sure your computer is not (just) a variable fan heater.

 

[Noriaki]

No they don't draw the maximum power at all times.

If you have a PSU rated at 150Watts that the maximum it can draw.
It won't be likely to draw that much power. Even Athlon boxes won't, their power problem is having enough power on certain lines, but they won't usually max out the entire PSU.

The only way to really know is to stick a volt and amp meter in there.

 

[mcgi6ah2]

Just depends on components, if your components add up to more than psu max, then off goes the psu, fuse if its a posh one, otherwise smoke time.

 

[R0b0tN1k]

A power supply at full capacity will output less power than it draws in. They aren't 100% efficient and do produce a lot of heat, which is why they have had fans built in ever since the first PC's. The power supply should have an input power rating indicated on it somewhere.

 

[4824guy]

Somebody will have to measure the current that the unit is drawing. This subject has been asked a few times and no one has had the time to measure this I guess. It would be nice to see how much a PC draws while idle and while being used. If I have a chance over the next few days I will measure this and post if if someone else doesn't do so before me.

The formula for wattage used is
Power used(watts) = supply voltage (117volts for US) times current flow (amps)

 

[Howard]

W = VA

i think