How much watt do I need for my system?

[hohyss]

I am currently trying to get

ASUS P5Q pro
Q9550 Yorkfield
8GB ( 4x2 gb ) DDR 800
Radeon HD4870
Antec 900 Case
Arctice freezer 7 pro
2x SATA HDD



I have a feeling that I might need at least 600w
but Im not quite sure how this is going to turn out.

How much watt do you guys think i need?

 

[Onus]

There is a PSU sizing calculator at http://www.extreme.outervision.com/psucalculatorlite.jsp. I would recommend adding 25%-30% to allow for some future upgrades and to put the PSU in a more efficient part of its operating range.

 

[jeb1517]

600W is more than enough.

 

[aevm]

Get a Corsair 750TX. High quality, only $100 at newegg these days, and it will support adding a second video card later. Your MB and case are already fine for that.

 

[dirtmountain]

I got about 450w for your system mildly overclocked with a couple of sensible peripherals. I'd go a quality 650w PSU. Can't go wrong with aevm choice of 750w Corsair

 

[hohyss]

I see. I usually turn comp on 24/7. But don't I end up paying more
elect bill for getting 750w? What will be the difference in elec bill for using 600w and 750w assuming that I turn comp 24/7?

 

[aevm]

No, a bigger PSU does not consume more. That's a max amount possible before it blows up, it's not the actual amount consumed. Just because a PSU is rated as able to deliver as much as 750W on demand, doesn't mean it will consume 750W. It will consume as much as your CPU and GPU and hard disks ask it to provide, divided by the efficiency.

For example you can get a 600W PSU with 80% efficiency or a 750W PSU with 81% efficiency and end up paying MORE with the 600W PSU. For example if your PC needs 400W, a 600W PSU with 80% eff. will consume 400/0.8 = 500W, and the 750W PSU with 81% eff. will consume 400/0.81 = 494W.
See how the max amounts (600W, 750W) don't even appear in the calculation... Over a year, the second PSU will save you 52 KWh, which is about $8 where I live. What you need is a PSU with (a) enough max power to cover future upgrades like Crossfire or more disks and (b) high efficiency

 

[hohyss]

Got ya. Thanks