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question about PSU wattage

FRATH
  • 2 months ago

Greetings to all, this topic has been talked and discussed millions of times before, I did my homework and know a bit or two about PSU calculations and system building. But still curious about your valuable opinions, I know how to use PSU Calculator websites etc, and have enough knowledge about to dig into the manufacturer websites and check the technical data for the components I intend to use, and make an approx. guess about the wattage I need for my build. But I am going to ask you anyway, because I love to learn and I am sure there are lots of people out there with wonderful information and background. So here is my question;

this is my build : https://pcpartpicker.com/list/2bWJwh

I am confused about the PSU selection, whether I should go for 750W or 850W? I am thinking about buying be quiet! dark power pro 11 750W or 850W. It is obvious that both 750 or 850W shoud be enough for my rig. But which one would be more efficient and produce less heat? I am leaning towards to the 850W but I just have basic information about workload and efficiency of PSU, I want to take advantage of your wisdom about this subject. Which one would you prefer and why? Or maybe you can tell me to forget both and buy a 650W PSU, one psu calculator website gives me about 600w of need, while the other one tells me some different story... I am confused and curiosity is building inside me badly...I am open to all ideas, but just tell me "why" please, why your opinion will be valid over the other wattage psu etc, I dont need a convincing, just want to learn the magic behind that watt and efficiency stuff... I wanted to ask about this topic here because I am not waiting for just "this one is good this one is not" type of answers, I am after "this one is better to that one because of "these factors" " type of answers..I want to learn and understand at the same time. Than you for your valuable time and have a wonderful day :) and sorry for any errors since English is not my main language.

Comments

  • 2 months ago
  • 1 point

The pcpartpicker estimate is usually not too far off from the maximum peak draw of the build. It will be a fair bit more than the normal draw even when loaded because it's rare to have both CPU and GPU maxed out simultaneously. Some CPU's pull more power than the rated TDP figure would indicate, but IMO that effect is only an issue for overclocked 9900K's and to a lesser extent 9700K's. (and we're talking about an extra 25-50 watts in general.)

So, your list would run fine on a 550w PSU. Moving to 650w would give you a bit of extra headroom, but there's no real benefit that I can see to going higher.

Some people will tell you to size the PSU to double the load, thinking to hit the top of the PSU efficiency curve, but I think that's a mistake; PSU efficiency curves are very broad and if you're concerned about efficiency, you would do better to move up to 80+ Platinum or Titanium. In any case, your list will likely draw an average of 300-ish watts under a realistic load, so 550w and 650w units aren't far from that efficiency peak anyway.

Given two PSU's X and Y, the question of which one will run cooler on a specified load is purely a question of where you are on the respective efficiency curves. If you happen to hit, say, 90% on both PSU's, they will generate the exact same amount of heat, even if one is rated 550w and the other 1000w. (The 550w unit might have to run its fan harder to get rid of the heat, since it would have smaller internal heat-sinks; but the total amount of heat will be identical.)

  • 2 months ago
  • 1 point

Thank you very much. The main question mark inside my head, was the one related to the "double the power of your PSU to the given max system wattage need, in order to reach the %50ish power" issue. There are people say that this will be the best way to use the PSU efficiently, the one and only plausible part of the whole idea, to me, is; "if you have a certain amount of higher powered PSU in your system, you will less stress the PSU compared to the closer rated wattage PSU, and it may be a slightly better approach to system lifespan and heat control, maybe... But not too much gap, only a small increment will be enough. This seems like overthinking actually, but this part of my system is the one that I have least knowledge about. this will be my third system and my other serious one has a gtx1080ti and 7700k inside, and I put a 750w fsp hydro g in it. Did not think about this issue back then, but the new system that I put here, is mainly for HTPC and gaming combined, and it has to be silent and low heat as much as possible, so thats why I tend to overthink every single aspect of it. I even tested two fanless aluminum chasis and one compact one, none of them gave me the satisfactory results, so I have high hopes with this one. Thank you very much for your reply and have a nice day.

  • 2 months ago
  • 1 point

If cost is no object, the best PSU for you might be the Seasonic 600w Titanium Fanless. Expensive, but very efficient, and you can't beat the noise level!

  • 2 months ago
  • 1 point

I also checked that, thank you very much for your comment, but I think PSU has to have some kind of active cooling just in case things get warmer inside, I am planning to install my system inside a TV cabinet and make holes for 140mm fans to work as exhaust and intake at the back side of the cabinet. So I want cool operating temperatures with minimal noise, I think it is better to have some high performance and silent fans to work quietly and help circulating fresh air. Fanless design rely on good open ventilation areas, so it wasnt an option for me. Thanks anyway

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