EggXpert

I just went through neweggs power supply calculator and it gave me a number I didn't expect. The amount of power it recommended was 1,580W! I was shocked considering I am going to try and build a 1 video card computer without a lot of extras. Anyways I went to another calculator listed on these forums and it said I only needed about 300W. Is neweggs calculator broken? Why would it recommend so much power?

Here's a screenshot:

link to larger pic: 

http://farm3.static.flickr.com/2427/4026717763_783469909d_o.png

LOL! They're both wrong.. You can't run a GTX 260 on only 300 watts and 1580 is about 3x what should be recommended...

GTX 260: 190 watts
CPU (motherboard supports CPUs up to):  150 watts
RAM + Chipset: 25 watts
Hard Drives, DVD-ROM, etc.: 20 watts

Sum:  385 watts..

Now of course, you don't want to be pushing your PSU to it's absolute limits, otherwise it will overheat and lead to early failure..  Best to target about 60% power usage on your PSU to allow you to do upgrades and to keep your power supply's AC->DC effieincy high..  80+ efficiency is only achieved between 50%-80% usage typically..

X(.60) = 385 watts

Solved for X = ~640 watts recommended PSU. And of course, I always recommend an 80+ certified PSU that's recommended in the EggXpert tier'd PSU list at the top of this forum.

Now what is required? Probably not more than about 450 watts so long as the PSU is flexible enough to deliver that power to the graphics card.. Of course, that pretty much guarantees you lose out on some serious upgrade options and also sacrificing AC->DC conversion power efficiency from pushing the PSU's caps closer to their max..but if you never throw in a power hog of a CPU, and you never run SLI, and you never upgrade your graphics card to something that pulls down more power, and you don't care at all about power effieciency and heat lost inside the PSU,  you might be just fine with a 450 watt PSU..  I certainly wouldn't recommend it though.

JJWeatherman:

Yeah I was planning on a 500W PSU but since you know a lot more about these things than me I may bump it up to the 600W range. I was really shocked when I saw that 1,580W though, lol. I think newegg better take a look at their system.

Yeah, I've been complaining about that system for years.  I even offered to help them fix it up, and update the wattages.  

Really, it's so easy to do a wattage calculation yourself, there's no reason to use a mysterious black-box power supply calculator.   When I get some time, I'll put a guide up here on how to calculate your needed wattage. 

---

Sidicas:

LOL! They're both wrong.. You can't run a GTX 260 on only 300 watts and 1580 is about 3x what should be recommended...

GTX 260: 190 watts
CPU (motherboard supports CPUs up to):  150 watts
RAM + Chipset: 25 watts
Hard Drives, DVD-ROM, etc.: 20 watts

Sum:  385 watts..

Now of course, you don't want to be pushing your PSU to it's absolute limits, otherwise it will overheat and lead to early failure..  Best to target about 60% power usage on your PSU to allow you to do upgrades and to keep your power supply's AC->DC effieincy high..  80+ efficiency is only achieved between 50%-80% usage typically..

X(.60) = 385 watts

Solved for X = ~640 watts recommended PSU. And of course, I always recommend an 80+ certified PSU that's recommended in the EggXpert tier'd PSU list at the top of this forum.

Now what is required? Probably not more than about 450 watts so long as the PSU is flexible enough to deliver that power to the graphics card.. Of course, that pretty much guarantees you lose out on some serious upgrade options and also sacrificing AC->DC conversion power efficiency from pushing the PSU's caps closer to their max..but if you never throw in a power hog of a CPU, and you never run SLI, and you never upgrade your graphics card to something that pulls down more power, and you don't care at all about power effieciency and heat lost inside the PSU,  you might be just fine with a 450 watt PSU..  I certainly wouldn't recommend it though.

Your numbers are a bit off there.  The GTX 260 is only rated for a power draw of 171watts, and even in the most intensive real world testing, it only draws 166.2watts.  Then, the motherboard supports CPU's with a TDP up to 140watts, not 150watts.  AMD does not make CPU's with a TDP higher than 140.  And, the CPU that he picked out draws 95watts.  For the hard drives/DVD drives, you need to factor in 10watts for each hard drive, and 25watts for each optical drive. 

So, corrected max wattage, assuming one hard drive and one optical drive: 

326watts

and, a good 500watt power supply would be fine for that system.   You can easily do that for <$50 after rebate(or get a 700watt modular for $50 AR), so no need to worry about having to spend a lot. 

---

That calc seems bugged for Phenom X3.   Select X4 instead and it drops to 540W.

scorrpio:

That calc seems bugged for Phenom X3.   Select X4 instead and it drops to 540W.

 Well, while that is closer, it's still more than 200watts off. 

---

if you want a more indepth look at the power usage of a system use this calculator

http://extreme.outervision.com/psucalculatorlite.jsp

 its actually the same one newegg, corsair, and BFG use.. they just simplified some of the information..