Solved How many watts do I need to power my desktop?

June 4, 2011 at 22:40:52
Specs: Windows 7
Okay, so this is my first time building a computer, and I'm not sure how many watts I should need to power everything. Here are the specs of my current setup:

Motherboard: BIOSTAR A880G+ AM3 AMD 880G HDMI Micro ATX AMD Motherboard (microATX)

Processor: AMD Phenom II X2 555 Black Edition Callisto 3.2GHz Socket AM3 80W Duo-Core Desktop Processor

RAM: ADATA 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666)

HDD: Western Digital Caviar Blue 500GB 7200 RPM SATA 6.0Gb/s

Wireless Adapter: Zonet ZEW1642D PCI Wireless Adapter

Optical Drive: LITE-ON 24X DVD Writer Black SATA Model iHAS424-98 LightScribe Support

Case fans: x1 80mm Purple LED fan, x1 120mm purple LED fan

Video Card: SAPPHIRE 100322L Radeon HD 6450 1GB DDR3 PCI Express 2.1 x16 HDCP Ready Video Card

Case: XION AXP 100 Gaming Series AXP100-001BK Black Steel ATX Mid Tower Computer Case

I initially ordered a 350W PSU because I wasn't sure what needed power, and when I received all of my hardware, I saw that my Video Card required me to have at least 400W power supply, my processor needed me to have 80W, my motherboard didn't specify. I just did a Power Supply calculator on Newegg, and I have my CPU, Motherboard, Opt. Drive, HDD, RAM, and Video Card requirements added up to at least 274W, but I'm not sure how much more wattage I'll need to power up anything else.
Any suggestions and help is very much appreciated!

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June 4, 2011 at 23:07:49
✔ Best Answer
You need a decent Power Suply with around a 30A Single 12VRail minimum , stating Watts is irrelevent, also you need to spend upwards of $50.00 on a PSU

Corsair are very good and highly recommended, spend as much as can afford:

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June 4, 2011 at 23:24:26
Thank you very much. :D I was leaning on buying a Corsair, because I heard they make really good stuff and hardly ever fail. I can definitely afford $50 for a decent power supply.

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June 5, 2011 at 08:12:13
Have a look at the link below. $40 after rebate.

The graphics card you chose is a low power consumption card. If you decide to upgrade that card to something requiring more power you may want to buy more amps on the 12V rail now.

Get a PSU with a single +12V rail. is an excellent online vendor.

Read the reviews and look at the warranty period, which are all available on the newegg site. Even Corsair makes PSUs of different quality. That is reflected in the warranty.

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Related Solutions

June 5, 2011 at 08:36:36
Yup, Newegg is where I got all this stuff for about $600. :) I know how great it is. I actually looked at that PSU, and decided to go up to 600W to this PSU: Which is exactly the same model, but with more amps on the 12V rail and more watt output.

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June 5, 2011 at 08:42:10
That Corsair unit has a 5 year warranty too.

When calculating power needs you need to look at the individual rails. On modern systems the +12V rail is the most important and on cheap PSUs the one most likely to be underpowered.

Graphics cards primarily pull from the 12V rail. When looking at requirements you can divide the load wattage specs for the GPU and divide by 12 to get the 12V amps.

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June 5, 2011 at 21:30:43
My comprehension of that second paragraph wasn't that great. XD So, what you're saying is that I should take 400 watts (the recommended PSU wattage to power my GPU) and divide by 12 to get how many amps I need?

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June 6, 2011 at 04:12:37
What I am saying is to ignore the 400W requirement because it is kind of meaningless. The cheaper the 400W PSU the less Amps it will have on the 12V rail.

Best to add up all the hardware that uses 12V primarily and if the current draw for the item is in watts, divide by 12 to get the amps.

That is why the poster in #1 above stated the required amps on the 12V rail.

Many PSUs have multiple 12V rails. The problem with that, while good in theory, is that some rails may not supply enough power, while others supply a surplus. That shows up when using top end graphics cards. Some of which draw 270W (270/12 = 22.5A@12V). While some hardware runs off the 5V or the 3.3V rails, those rails usually supply too much amperage.

So most helpers here recommend a single +12V rail active PSU. 30A on the 12V rail is a starting point for systems with an add in graphics card and a decent CPU. Systems with 2 graphics cards may need 60A.

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June 6, 2011 at 09:51:07
Oh okay, I got you. So, do you think my Corsair CX600 600w single 12v rail @40A will be fine for my setup? I went ahead and placed my order for it last night.

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June 6, 2011 at 12:42:19
Yes it will.

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June 6, 2011 at 21:19:31
Thanks for all your help!

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June 7, 2011 at 04:35:13
You are welcome.

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July 5, 2011 at 19:36:42
Yes, everything works flawlessly! (and has been for about 2 weeks. :3)
Thanks again for all your help.

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July 6, 2011 at 04:55:32
Glad to here that. Thanks for letting us know.

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