PSU - Supplies All Power??

[Oddsk8er]

I have been told by some people that if I had a 500 watt PSU and only had a system that pulled out 300 watts, the power supply would only take out 300 watts (Therefore, if the only electronic device in my house was my computer, I'd only have to pay for as much as the computer was on for 300 watts). But I have also been told that if I had a 500 watt PSU that the PSU will ALWAYS take out 500 even if my system only requires 300 (In this case, I'd be paying for 500 watts of power no matter what is in my computer).

Which is the case? I don't want to end up buying a power supply that is too much for me if I don't even need that much power. And I don't want to waste energy. But, If the power supply only takes as much as it needs, then I'll go for the 500 watt.

 

[sithspawn]

Well look at it logically, to be drawing power you need to have a complete circuit. If you have only 300W worth of stuff plugged into your PSU, then only those circuits that are completed (plugged in) will be drawing power. Its not like there are loops setup inside the power supply that just constantly draw power. Make sure the 500W PSU you are getting actually supplies enough current to your seperate rails though, a problem a lot of people dont bother about (having a 500W power supply doesnt automatically mean it will be able to power all your current usage).
Go here if you want to know more about what im saying:
http://www.firingsquad.com/guides/power_supply/page2.asp

 

[WQ87]

I believe it was made to take out as much as your computer would need. So if your comp requires 300watts, then the PSU will try to bring in the exact 300watts. It will only reach 500w if your computer need it. These PSU are design to save energy, i mean an extra wasted 200watts, that's going to cost you something for nothing.

 

[kboy]

Try this link to determine your actual power needs, Myself I'd just go with the 500, Ya may need the additional power in the future when ya add additional hardware to your Box.


http://www.jscustompcs.com/power_supply/

 

[Oddsk8er]

haha, I just had a stupid argument with my friend about this. Then I check my email saying people replied and looks like there are 3 people who said what I was thinking.

But yeah, I figured it was the first case, but I have had several people tell me they were sure that the power supply takes 500 watts no matter what and I just found that to be stupid.

 

[killians45]

Yeah, it only pulls what it needs.

 

[killians45]

Thought it could only pull 120 since thats the standard wall output? Think it just uses capacitors and switches in the PSU to regulate the voltage and the output from the PSU will only supply what is needed IE putting in a 500watt will not damage the components because they draw only what they need. Guess I read the post wrong However, if I understand correctly they ALWAYS pull in some 5 or so while plugged in for power on... could be wrong on that count, though...