Power Consumption Question

[blahsome]

Sorry for the newbie question, but for all you electrical majors out there...

Once turned on, will a 300W PS always consume 300W of energy regardless how many devices are using it?
In other words, will a 400W PS consume more energy than a 300W one for the same system configuration?

Thanks.

 

[mothman]

A 300W PS means it can supply 300 watts of power.
A 400W PS means it can supply 400 watts of power.

Watts are volts x amps.
example: A device running at 12 volts needs 1.5 amps.
It will need 18 watts of power. 12v x 1.5a = 18w

How much power you use depends on what you have
connected to the power supply.

Devices hooked to a 300w PS use the same power
if hooked to a 400w PS.

Hope this helps....

 

[blahsome]

Thanks! This makes perfect sense too. I was arguing with a friend who insisted otherwise. He sounded pretty authoritative though.