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Sorry--basic PSU question

B

bssman

Weaksauce
Joined
Aug 16, 2004
Messages
89
Am building a new computer and have a basic question concerning PSU's. According to a PSU calculator I will only be drawing 250-275 watts of power. There are some PSU's here on the "for sale" forums that are very tempting. One is the Thermaltake Toughower 650w which looks pretty good and efficient. My question is 650W is probably overkill for me, but if I don't use all that power am I wasting electricity?? IAW would a similar 450-500W power supply use less electricity because it it rated at a lower output?? No sense in purchasing a larger PSU if it's only going to waste electricity! Thanks for any input!
 
A power supply only puts out as much power as demanded from it.

That said, efficiency will vary depending on load. PSU's are typically more efficient at 20% load and up. But, a good PSU can still be more efficient at 10% than a cheaper, smaller one at 20% or 50%. So don't automatically assume that because you're using a 450W with 50% load that it's more efficient thana 650W @ 20% load.
 
Thanks for the reply! The Thermaltake I'm looking at is advertised at 650W, 85% efficient so IAW if I'm only utilizing half it's output it would still be cheaper to run than a 450W, 70% efficient PSU. Believe I have that correct!
 
Again, efficiency will vary depending on load. When Thermaltake says the PSU is 85% efficient, that's at it's best. It's probably a lot less than that when the load is < 10%. THAT SAID, that doesn't mean a 450W at 50% or more is more efficient. Some units are more efficient than others at different loads. One must compare apples to apples.
 
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