What size PSU should I get?

[biton161]

Hi,

For my miniITX build I'm debating between the 300W vs 450W Silverstone SFF:

https://www.amazon.com/SilverStone-...UTF8&qid=1513106047&sr=8-1&keywords=st30sf+v2

https://www.amazon.com/SilverStone-...ie=UTF8&qid=1513104156&sr=8-1&keywords=st45sf

According to this calculator the total Wattage shouldn't exceed 260W:

Motherboard: Mini-ITX
CPU: 1 x Intel Core i5-3570K 3400 MHz Ivy Bridge CPU Speed: 3400MHz CPU Vcore: 1.25V CPU Utilization: 90%
Memory: 2 x 4GB DDR3 Module Video Card Set 1: 1 x NVIDIA GeForce GTX 1050 Core Clock: 1354MHz Memory Clock: 1752MHz Core Clock: 1304MHz Memory Clock: 1702MHz
Storage: 1 x SSD
Storage: 2 x SATA 5.4K RPM
Keyboard: 1 x Standard Keyboard
Mouse: 1 x Standard Mouse
Fan: 1 x 92mm
Fan: 1 x 120mm
Computer Utilization: 8 hours per day Gaming/Video Editing/3D Rendering Time: No Gaming / 3D Apps Monitor: 1 x LED 24 inches

Load Wattage: 209W Recommended Wattage: 259W Amperage: +3.3V: 4.3A, +5V: 7.3A, +12V: 17.3A Recommended UPS Rating: 500VA Generated by OuterVision PSU Calculator 2017-12-12 03:05:44

Is the 300W too marginal? if it is possible I'd prefer the 300W but I don't want to take uncecessary risks...

 

[UsandThem]

Hi,
Is the 300W too marginal? if it is possible I'd prefer the 300W but I don't want to take uncecessary risks...

While calculating your components, it appears you should stay under 300w. However, for your PSU to perform at peak performance (usually in the 40% - 70% range), you would need to get the 450w. With the 300w at full load, you would be out of that range.

Even the EVGA calculator (which is usually among the most accurate out of all the online calculators) recommends a 400w unit. You can always get the 300w and see how it goes.

https://www.evga.com/power-meter/

 

[MaikuTech]

What kind of case do you have by chance ?

 

[Mr Evil]

...for your PSU to perform at peak performance (usually in the 40% - 70% range)...

Peak efficiency is around there, but most PCs spend only a fraction of the time at full load. Mostly they are near idle, and smaller PSUs are usually more efficient there.

 

[UsandThem]

Peak efficiency is around there, but most PCs spend only a fraction of the time at full load. Mostly they are near idle, and smaller PSUs are usually more efficient there.

True. But if is placing a high load on it 8 hours a day, like he mentioned in his original post, that is the part to be concerned with.

If he was building a PC to browse the internet, check emails, and other general use, I'd say you are absolutely correct. He would likely never pull more than 150w.

 

[UsandThem]

Also, one final note in this thread. If you look at the two power supplies he listed in the OP, one is $50 and the other is $60.

$10 extra is worth the peace of mind, and not have to worry in case they ever upgraded or add more components.

 

[DrMrLordX]

There are two old schools of thought on this matter.

The JG method mandates that you should get a PSU that can handle twice the maximum expected power draw of your system. The other way is to get a PSU rated so that the maximum expected power draw is no more than 80% of the PSU's capabilities. 400W is closer to the JG method so you won't go wrong there, at least not on account of the wattage.

You should also be looking at efficiency and expected PSU life. Some of the lower-wattage PSUs use lower-quality components and are somewhat more prone to failure during normal use than higher-wattage units.