How much PSU wattage you need for your PC

 Last year I published an article teaching how to pick a good PSU. While the main reason for that post was amount of people buying E and F tier PSUs, there's also a fair share of PC builds I see where people spend too much on higher wattage PSU which compromises their budget for other components. But, at the same time, there are some people who buy a PSU that isn't powerful enough. 

Out of the aforementioned 2 types, people who buy higher wattage than needed are on safer side, but like I mentioned, it often cost them a large amount of their budget. Specially in India where average salary of people is often less than the cost of a decent budget gaming PC, it becomes a big problem. 

So why do people make mistake of calculating their wattage wrong? There are two big reasons. 

  1. There aren't many definitive guides out there for wattage calculation.
  2. The online wattage calculator results are all over the place.

Also there is one more reason that affects people choice: PSU efficiency rating. It is now a somewhat known fact that PSUs are most efficient at 50% load. This knowledge drives many people to buy twice the needed wattage PSU.

Now back to 2 main reason, first one is hard to tackle as there are many unknown variables that can alter the actual wattage requirement. So no one can make a universally accurate PSU wattage calculator. This fact brings us to 2nd reason, the online PSU calculators. 

I used the same data on 4 PSU calculators, all 4 are from one of the major PSU manufacturers, You'd think that no one would know better than PSU manufacturers themselves, right? Well technically none of them provided wrong results, but one of them was really questionable. 

Let's discuss the PC build in mind first

  • CPU: Ryzen 7 7800X3D
  • Cooler: Deepcool AK500(I know that it is barely enough but stay with me, this isn't a CPU cooler guide)
  • Motherboard: Any standard ATX motherboard with 2 or more M.2 NVMe slot
  • RAM: 32GB(2x16GB) DDR5
  • Storage: 1 M.2 SSD for OS and software, 1 M.2 SSD for games and 1 SATA HDD for mass storage
  • GPU: RX 7900 XTX
  • Cabinet: Any standard cabinet with 3 pre installed fans

Now from what I know about PC parts, the max power draw of above configuration would be 600-650W at 100% load. But just to be on safe side, I'll recommend 750W or higher for this build. Let's see how these PSU calculators performed.

First, the questionable one

So why am I calling it questionable? First, it doesn't account for CPU cooler and case fans. Then it recommends products that are more than adequate(plus point there) but pricing and availability are not so adequate. If I were a PC building noob, then I'd think since my PC's power draw is 566W. any 600-650W PSU will be sufficient. And while the PC would work fine with 600W PSU, there will be times when the PC will draw over 600W which could trip one of the protections(mainly OPP).

Next one is from Seasonic

This one is also little bit questionable in my eyes but I'm giving it better score than Cooler master because it also considers system fans. It recommended 850W minimum so it didn't do that bad overall, but like I mentioned, my calculation says 600-650W draw, but it didn't show how much wattage the PC would draw, so I deducted some points there. 

Next is MSI

It gained more points for considering additional PCIe expansions as well, but lost points for overestimating wattage required. Again, no harm in having extra juice but MSI is kinda making the customer spend extra. 

Next is Be Quiet

If you couldn't tell by seeing more pictures than others, this one won my vote. I'll be honest, I don't rely on PSU calculators so I never used any of them before starting this article. I'm totally blown away by how good be quiet made this calculator. Yes, it still overestimates a little but not by a huge margin, in fact I'll call it sensible calculation considering some GPU models are factory overclocked and some fans draw more wattage than others to achieve higher RPM.

On top of it, be quiet gave you recommendations based on budget and quality.. I'm struggling to find right words to praise them, so I'll just say, "Excellent job Be quiet, please consider PCIe expansion cards as well." 

If they add PCIe expansion cards as well, it will be the perfect PSU calculator. But it is still excellent for average PC builders/users. 

I'll also let you know that it also recommended accordingly for a budget build(Ryzen 5 5600+RX 6600). 450-500W is enough for such build they included 500W PSU in the recommendation list. 

So if you a new PC builder and struggling to calculate the wattage, I highly recommend the calculator by Be quiet. 


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