• Date: September 26, 2018
  • Author: nejc
  • Category: Hardware
  • Comments: 0


One of the most overlooked components in a workstation build is usually the Power Supply Unit (PSU in short). What I see most freelancers and smaller studios do is to invest as much as possible into components such as the CPU, GPU or even memory kits and ultimately skimp on the budget for an adequate PSU. That is a seriously bad idea as a PSU that is not designed to handle the desired load will essentially buckle under the pressure and cause instability issues such as crashes, reboots and in rare cases it will even cause a premature death of other components.

Build quality is an extremely important factor that should not be overlooked. There are many PSUs out there and I would definitely recommend checking out reviews before buying.

That being said, this article will not focus on a particular brand of PSU makers nor will it go into any sort of detail of what makes up a quality PSU. Again, I would highly recommend checking out actual reviews of the certain PSU units in order to ascertain whether they are considered quality products by industry professionals.

This article will focus on how you can do the preliminary work of determining how much actual power (W) you need before you starting picking your actual PSU.

Each component in your workstation needs a certain amount of power (W) to operate. Be it the CPUs, the GPUs or the fans in your case. All of those need electricity to operate.

The common confusion comes from the fact that it can get confusing (not to mention time consuming) to determine how much power each component actually eats up.

Luckily, almost every PSU maker out there has some sort of a basic Power Supply Calculator on their website. Unfortunately though, some of them are quite basic up to the point where you cannot even choose the exact components that are in your system – Especially if you are running a high end workstation setup.

To that end, I personally recommend the following websites:

Please note that I am not affiliated with any of these and the order that they are listed in is random.

So how do these PSU calculators work and what is the caveat?

First off all, you need to realize that these are only estimates. They are not concrete values.

Each major component in your system has a specified TDP (Thermal Design Power) number which is usually used to get a W estimate. For example, AMD Threadripper 1950x has a TDP value of 180W. While that is probably the actual capped value by AMD you can obviously expect that value to go out the window once you do any form of overclocking. It gets even crazier for GPUs as you might have a 3rd party GPU that is overclocked and that by nature has a different TDP than the one listed in the PSU calculator. As far as GPUs go, PSU calculators usually list only generic, manufacturer graphic cards.

Sometimes the TDP isn’t even exact by itself and that is the manufacturers fault. So take that into the account as well.

That is quite a few caveats but for every workstation that I build I still use the above listed PSU calculators to get my estimates.

The calculators themselves are pretty easy to use. You just go over the menus and select the components that you plan on using. I usually set the CPU TDP value to 100% just to get a little more extra breathing room. If you plan on rendering on the CPUs then rest assured, the full TDP your CPU can muster will be in effect.

For all of you who are building a GPU workstation, please do not skimp on the CPU TDP. Yes, technically, once you start your GPU renderer the CPU will probably idle in the below 50% mark in terms of its actual usage – The TDP will also probably match that. That being said, open up your image editing software or continue doing something that is fairly CPU intensive and you’ll get spikes into the 100% usage area which means your CPU will for at least a few seconds operate at its peak on all cores. That means that even though you will be doing the bulk of your work on the GPU, the CPU will fire up too depending on the task at hand. You need to reflect that in the calculator by using a high TDP value for the CPU.

Treat the estimates as estimates. Once you get your estimate I recommend thinking long and hard about it and whether it is worth going at least 100W or 200W higher than what you actually need. Firstly, the estimate may be off and you always need to make sure there is enough power available for your workstation to use. Secondly, the components in your computer produce spikes that can go quite higher than the actual TDP ratings. Thirdly, your PSU is most efficient at lighter loads and so it will also produce less noise if you have enough headroom.

For example, I plan on upgrading my workstation that consists of a dual Xeon 2699v3 CPUs. I plan on adding at least two GPUs into the system. The estimate that the PSU calculator came up with rounded at around 940W. The PSU I would take based on that estimate will therefore be at least 1200W or preferably 1300W.

In reality though, I plan on giving myself some headroom for further expansions and so the investment will actually be made into a 1600W PSU. Expansions are something you should really think about since we all know unpredictable upgrades cycles can be.

Hopefully the article will be helpful to all of you who are trying to build a workstation yourselves but don’t know how to calculate your PSU needs. I’d like to stress this again, the PSU is a vital component of your workstation and always try to read up on the latest reviews of the latest gear.

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