# Thread: So - how to choose psu capacity, and WHY

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## So - how to choose psu capacity, and WHY

More I learn(of course still little), things keep getting complicated...

So considering all(as much as, internal, external...) factors behind, how much POWER should I get for a system, and why that much?
Should it differ by price range?

Further explanations would be great.
Last edited by rgbodosk; 05-24-2019 at 02:51 PM.

2. 1600W. Powers anything and everything.

3. As much as your system needs!

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bluehillday (05-25-2019)

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Originally Posted by Orion
As much as your system needs!
uh so complicated

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Estimate how much your computer will require, then add around 20-30% (just in case you'll add hard drives, or a more powerful/power hungry processor or video card)

If that's still below 400-500w, then go with whatever you want between 500w and 650w... because the price differences between 500w, 550w and 600w are usually very small.

A modern power supply is at its peak efficiency within 40%..80% of its maximum output.
While a modern power supply can produce its maximum output practically 24/7, you want to use the power supply at or near it's highest efficiency point, because the power supply will produce less heat and therefore the fans won't spin as much and you'll have a more silent computer.

So let's say when you're gaming, the computer will consume around 300 watts. 20-30% of that is around 100w, so you want a power supply that can provide at least 400w.

You also want that 300w number to be somewhere between that 40% .. 80% of the maximum output of the power supply. Let's go with 60% because it's a nice round number.

So if we want 300w to be 60% of the maximum output of the power supply then 100% is 300w x 100 / 60 = 500w.

So a 500w power supply would be more than enough for your computer... but feel free to go with 550w or 600w, whatever's with good efficiency, long warranty, features you need.

20-30w motherboard
15w per core cpu ( around 60w for a quad core, 80w for six core , 100-120w for eight core)
2-3w per memory stick
2w per fan
8w per mechanical hard drive
2w per ssd

video cards - up to 75w if they don't have any additional power connectors. add up to 75w for each pci-e 6pin connector, or 150w for each pci-e 8 pin connector. So for example a card with only one pci-e 8pin connector will consume UP TO 75w+150w = 225 watts.

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bluehillday (05-25-2019)

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