Beginners guide to sizing a power supply?

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Joined
7 Dec 2011
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51
There are quite a lot of posts giving a configuration and asking if a PSU will be big enough.

Is there a beginners rule of thumb to aid sizing the maximum power demand for a system?

I can see ratings for video cards, for example, but HDDs and SSDs can vary quite a bit and I have no idea which components I would need to add in the future.

Also the maximum power draw for individual components is likely to come at different times. For example on system start up the disc drives are likely to be pulling their maximum power to spin up the drives, but the video card is unlikely to be running at maximum power.

Any guidelines such as allow 25W for each HDD?
Any idea how much a motherboard draws and how much each memory stick draws?

I guess the experts have some kind of simple rule to be able to check the configurations posted here.
 
I have a 400W PSU.

I'm trying to work out if it will be big enough for this configuration.

My basket at Overclockers UK:

Total: £232.45
(includes shipping: £10.50)



Various pessimistic assumptions have got be up to around 300W but I have no figure for the motherboard and memory. Although I have a figure for the processor I have no idea if it includes the stock cooling fan.

I am assuming 6 * HDD at 25W peak power each, 4 case fans at 10W each.

I will no doubt need some headroom for attached devices drawing power from USB.

So - below your guideline of 500W.
 
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