PC power calculation

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Bruno Koob

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Feb 13, 2014
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I would like to know what kind of power supply Wattage I should get. I am looking at a 500W but is that too low? What if I want to overclock? Here is what I am looking on building. Thanks all!

i7 4770k – Intel
GA-Z87-HD3 – Gigabyte
CPU Cooler- Zalman CNPS950AT
Radeon R9 270x – Asus
2X8 GB 1600MHz DDR3 – Kingston
60GB SSD - Kingston V300
1GB 7200 rpm HDD SATA 6Gbs – Western Digital
DVD burner – Asus
Internal USB bus powered card reader
PCIE Firewire Card – Rosewill
External Firewire audio interface – Focusrite Saffire Pro 14
2x 120mm case fans


 
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hunter315


This is a silly statement considering most 450W units have 32A on the 12V rail. If you get a 600W PSU with 32A on the 12V rail you just got scammed hard core. The vast majority of a modern PCs power draw is from the 12V rail(80-90%) so you should make sure most of your power is available there, take the 12V current, multiply it by 12V to get the power available from that rail. 32A is 384W which is good for a unit in the 400W category, a 500-550W unit will usually be around 40A, 600-650 is usually 50A, and 750W units are usually about 60A available combined power of...
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Bruno Koob

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Feb 13, 2014
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wow, thanks. I didn't know that. What exactly am I looking for, the output amps for GPU on the power supply?
 
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Bruno Koob

Honorable
Feb 13, 2014
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Thanks.
 
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hunter315

hunter315

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May 12, 2009
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This is a silly statement considering most 450W units have 32A on the 12V rail. If you get a 600W PSU with 32A on the 12V rail you just got scammed hard core. The vast majority of a modern PCs power draw is from the 12V rail(80-90%) so you should make sure most of your power is available there, take the 12V current, multiply it by 12V to get the power available from that rail. 32A is 384W which is good for a unit in the 400W category, a 500-550W unit will usually be around 40A, 600-650 is usually 50A, and 750W units are usually about 60A available combined power of the 12V rails.

I'm with rolli on this, a good 500W unit will do just fine, a good unit will have ~40A available and will last you for several years. A poor "500W" unit will give itself away by lacking any 80+ certification, being rated in "peak" power, and having less than 80% of its rated wattage available on its 12V rail. If you ever stumble across a unit that has a surprisingly large amount of current available on the 5V rail, skip it and move on, it is from an older era when CPUs were powered from the 5V rail.
 
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Brantyn Gerik

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Sep 18, 2013
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The 12v rails only have what they specify in the spec sheet and you would be surprised how many don't, especially with a 450w unit. No reason to call it a silly statement when i can link probably 10 power supplies in the first 2 pages at newegg in the 450watt range with under 32amps on the 12v rail.
 
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rolli59

rolli59

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Oct 27, 2007
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Some are PSU's and some are PSU shaped objects. PSU 450 watts 34 amps +12 volts http://www.newegg.com/Product/Product.aspx?Item=N82E16817207018
PSU shaped object 450 watts 2 x 14 amp +12 volt rails http://www.newegg.com/Product/Product.aspx?Item=N82E16817148042
 
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