PSU - How does it work???

[navi310]

Hi All,

I have this question I couldn't find the answer to anywhere.
It's about PSU & how it operates.
For example if PSU is rated "power supply - 400 Watt" does this mean that it constantly consumes
400 Watt or does it depend on the System load??

I mean I bought a PC 3 years ago & it had 1 HDD & 1 DVD-RW. Than I upgraded a little and installed second HDD & second DVD-RW.

So my question is: did my PC before upgrade and now, after upgrade, use the same amount of power or it used less with less hardware and uses more with more hardware??

And another question: does an idle PC use the same power as the one working at 100% (e.g. video encoding)??

I know it's probably stupid question but anyway...

Thanks a lot in advance.

[SLK001]

The 400 watt rating it the maximum capable output of your unit. It is a switching power supply, so its actual output depends on the demand. With little load, a switcher consumes little power (they are >80% efficient).

[navi310]

Thanks SLK001 for your reply.

I'm not sure that I understand this correctly.
I mean this question has to do with Electricity Bills

Did I pay less for electricity consumed by my PC before upgrade or it was the same as now (after upgrade)?

Sorry if it sounds a bit confusing.

Thanks.

[jagabo]

Some examples of system power consumption at idle and load:

http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=3003&p=9

[SLK001]

If you increased the load on your PSU (by adding additional drives), then your electric bill will rise.

[jagabo]

Did I pay less for electricity consumed by my PC before upgrade or it was the same as now (after upgrade)?

There's no way of saying without knowing all the details of the systems, exactly how they were set up, and your usage patterns.

<edit> Oh, sorry, you only added stuff to an existing system. In that case you are probably consuming more power with the addition of more hardware. A possible exception would be if you changed power related settings. For example most CPU's now have special low power operating modes when the system is idle -- but the option must be enabled in the BIOS. Windows also has the ability to power down the hard drives when not in use.</edit>

[navi310]

Thanks a lot, everybody, for your help!