Power supply's watts

I have read some technical reviews about PS. But I have not seen yet one that guide me how many WATTS should I buy. (Links?....)

So how big should the power supply REALLY be (in watts)? Is there a thumb rule for that?

Is there any recommendations? (as "the bigger the better", or "every PS that has xyz characters better than one who has not")

Do you have some EXPERIENCE (real life please) with Brand Names? (Antec, HEC, Supermicro, Seventeam, Vantec etc etc)
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Well most cheap PC power supplies are rather optimistically rated. That is a 400W supply will not supply 400W continously. So as a general rule add up the average draw of all of your components, and multiply the result by 3.
For upper mid range pc this will be about 350W.
zolpoAuthor Commented:
"So as a general rule add up the average draw of all of your components, and multiply the result by 3. "

Can you explain please.
dbruntonQuid, Me Anxius Sum?  Illegitimi non carborundum.Commented:
The CPU manufacturers have recommendations on to how big the power supply should be.

Here is AMDs listing


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zolpoAuthor Commented:
dbrunton! That link is very good. Thank you.
here is a question I asked.  The fact that P/S are very misleading when they state how many watts it is.  There statements are true, but just misleading.


You will just need to sit down and figure out how many amps you will need for the 12v service.

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I had a cheap P/S and it just did not cut it.  The voltages were not as close to what they are supposed to be.  I purchased an Enermax and I am very happy with the ratings that I get now.  Enermax is also the quietest P/S that I have never heard.
When you buy a PSU, make sure it has line conditioning and voltage regulating.  Remember that any unit will have a decrease in power the hotter the ambient tempature is, and it can get quite hot in a comptuer case.  I hear that PCPower and Cooling has some high quality PSUs.  http://www.pcpowerandcooling.com/
Glen A.IT Project ManagerCommented:
Cheap power supplies rated at 300W, 350W, 400W and more generally aren't up to what they say they are.

AMD used to actually CERTIFY power supplies for use, but the testing cost them so much that they finally stopped.  They still maintain the list of manufacturers who had power supplies that passed.

Generally speaking though, Antec, Enermax, Sparkle are my three favorites for being excellent quality and providing more than enough for the job.  It's not just the wattage rating, but the reliability and consistency of the power supply to deliver continuous stable power across the rails.

I've seen cheap 400W power supplies that couldn't power a PC properly that, when replaced with a 300W antec worked just fine.

As far as a good calculator, http://www.jscustompcs.com/power_supply/ is a good one that works well as a general rule of thumb.
Glen A.IT Project ManagerCommented:
BTW, the link of vendors who've had psu's pass AMD certification is here: http://www.amd.com/us-en/Processors/DevelopWithAMD/0,,30_2252_869_1039^4038,00.html

however, keep in mind that not ALL of the psu's from these companies passed testing/certification, so some of the companies on this list may make power supplies that don't meet the specification anymore.

You can rest assured that many of them do, though.  just never buy the cheapest power supply, it's never worth it.
 >just never buy the cheapest power supply, it's never worth it.

I would agree 110 %

AlbertaBeef BTW i crawled out from under my rock for a while.
Glen A.IT Project ManagerCommented:
lol.  Got cold under there, eh?
zolpoAuthor Commented:
Thank You all!
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