Is a 300W PSU too small?

I am looking at building a small computer with lowest possible power consumption, here is my parts list:

Corsair CMV4GX3M1A1333C9, 1x4GB, DDR3-1333, PC3-10600, CL9, DIMM

In Win BL641 Desktop Case, 300W PSU, Black/Silver
Western Digital Caviar Green WD20EARX Hard Disk Drive, 2000GB, 5400-7200rpm, 64MB Cache, SATA 6 Gb/s
Gigabyte GA-H77M-D3H Motherboard, Socket 1155, Intel H77, 4xDDR3, 2xPCIe-16, 1xPCIe-1, VGA, DVI, HDMI, RAID, M-ATX
Intel Celeron G530 2.4 GHz, Socket 1155, Retail pack with fan, Sandy Bridge

According to the Gigabyte manual there may be issues with a PSU lower than 500W, but as you can see from the above parts list, the slim In Win BL641 Case only has a 300W PSU. The exact wording from the manual is below:

To meet expansion requirements, it is recommended that a power supply that can withstand high power consumption be used (500W or greater). If a power supply is used that does not provide the required power, the result can lead to an unstable or unbootable system.

Considering the components I am using, I am not sure I actually require a bigger 500W PSU. The only expansion I plan in the future is adding 2 additional low power HDD’s and another stick of memory.

I've calculated the the power consumption of my components based on the information I could find with the exception of the actual mobo:

2x Ram: 2 x 8 = 16W (at most)
CPU: 65W (TDP)
3x HDD: 3 x 6 = 18W

Total: 99W

Is it likely a motherboard will use more than 200W of power?

EDIT: Formatting

surfisup1000

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#621738 8-May-2012 15:58

I reckon you'll be fine . Unless you 'expand' your system. You're using internal gfx . Of course, you won't be able to expand with a high end gfx card in future.

sidefx

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#621753 8-May-2012 16:29

Depends very much on the PSU I would say. I've owned a couple of Shuttles, with 220\250W PSUs that handled fairly grunty systems without any issues.

At the same time budget PSUs can have trouble with fairly moderate systems even when rates at 400\450W+; all depends on the quality.

I'd also be looking for headroom if I were you... your estimates look a bit low on the HDDs and also ignore fans\optical drives(?)\any other PCI cards\USB\other PCI,PCI-E cards\etc

And I think most PSUs are not 100% efficient and perform best\most reliably when running at <70% of their rating.

EDIT: maybe try a PSU calculator? http://extreme.outervision.com/psucalculatorlite.jsp

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freitasm

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#621770 8-May-2012 16:51

You haven't said anything about video cards? In any case, I have a Lenovo desktop here with 240W PSU, 2x4 GB RAM, SSD, Intel Core i3 and installed an ATI Radeon HD5450 (low profile because the Lenovo ThinkCentre is a small case) with no problems.

I guess using the SSD instead of a HDD help reduce the power consumption a little bit too.

mroarsome

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#621777 8-May-2012 17:14

I will be running the on-board/cpu graphics. I'm not planning on using this for anything graphically intensive, basically the computer will be a file server as well as running a few remotely accessible applications at home.

I want the build to be as energy efficient as possible and ideally small form factor as it will be sitting in my home theatre cabinet (well ventilated). I require some pretty specific x86 applications to be running all the time so a NAS is not a solution for me - although a decent NAS is not too far off this price point anyway.

It looks like yes, I was a few watts off on my HDD estimates, they actually run closer to 8W, but in the scheme of things this doesn't really make a difference.

I think I will just go for it - if all else fails I can on sell the case (or keep it for another project) and get a new one.

Will order it tomorrow - you might here from me again when it all ends in tears (or hopefully smiles)

mroarsome

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#637668 8-Jun-2012 09:44

Just a quick update. Computer has been built and running now for 2 weeks and so far stable. Measuring from the socket using a Mains Power Meter the system is drawing around 55W (VA) under load and surprisingly 14W (VA) on standby.

I'm pretty happy with that result!