15 MAY

Tech Help - What wattage PSU do I need for my server?

Published by Richard Parry on 15th May 2019

Something we get asked often is what wattage PSU is needed for a server.

One thing to immediately know is that a desktop/PC power supply is not as powerful or efficient as an industrial/server grade PSU, so I wanted to create a comparison chart between a desktop and server PSU to get started;

Desktop PSU Server PSU
  • Low cost
  • Easy to replace
  • Readily Available – Most online PC retailers will stock them
  • PSUs usually have a peak capability for a short amount of time – an advertised 500W PSU could not sustain 500W peak for an extended period – It’s likely around 400-450W is the usual maximum sustained power output.
  • Some lower end models may have poor voltage ripple, which can cause stability issues if used with certain server-grade components such as motherboards and CPU.
  • Low MTBF
  • No redundancy capability
  • Not designed for 24/7 operation
  • Limited warranty
  • Higher price
  • Usually made out of a thicker steel
  • Sometimes harder to obtain in the event of a failure – we often keep a large stock though
  • Most do not have a peak-wattage and will be able to run at their advertised capacity indefinitely without degradation in lifespan or performance.
  • Low ripple/noise so works well in sensitive applications with server grade motherboards/CPU
  • High MTBF
  • Redundant PSU options available in dual, triple and quad configurations for full high availability.
  • Designed for 24/7 operation – hot-swappable PSUs in redundant PSUs allow continuous use without interruption.
  • Usually 3 year warranty on more premium brands.

Hopefully the above comparison helps you identify if you want a desktop or a server grade PSU. The most important element is to think about uptime. If you can afford downtime to replace a PSU in the event of a failure, which is more likely to happen with a desktop PSU and you have a limited budget then a desktop PSU is the way to go. If you cannot afford the downtime, then you should look at a server grade PSU and ideally a redundant model. I’ve written an article recently on Redundant PSUs here; https://www.servercase.co.uk/blog/article/tech-help---how-does-a-redundant-psu-work-and-what-are-the-benefits/

Now you know what type of PSU you need then let’s get down to choosing the right wattage. To help with this I’ve created a chart for common components and what power they use;

Component Wattage
CPU 100W
RAM 5W 
SSD  10W 
Motherboard  30W 
HDD (each) – 4 HDD’s  10W Each (40W Total) 
Fans  30W 
TOTAL  215W 

So in the above example we’ve chosen a reasonably powerful CPU, that might end up being a Core i5 or perhaps a Xeon with a reasonable specification. RAM uses barely any power and neither does SSD’s. The motherboard has various components which will use a reasonable current and in my example,  I’ve gone for 4x HDD.

In total our example uses 215W, which is fairly conservative – Under load the CPU will draw slightly more current, the fans will need to speed up and use more current and higher HDD load may increase the current draw on those too – so for this system you may be safe with a 300W maximum amount.

Today generally the smallest PSU you can buy is around 300W in desktop PSU grade and 500W in server grade.  My suggestion for this setup would be a 500W PSU in desktop and 500W PSU in server grade. This will mean low stress on the lower-quality desktop PSU and add longevity and it will run very comfortably with a 500W server PSU.

To help even further I’ve made a small chart which I think will be helpful.

Load in Watts

Desktop PSU Recommended Watts

Server PSU Recommended Watts

300W

500W

500W

400W

600W

500W

500W

750W

600W

600W

850W

700W

700W

1000W

800W

800W

1200W

900W

900W

1300W

1000W

1000W

1400W

1100W

 

I need some more help

Sure – We are here to help and recommend the right components for you – All we need to know is the components in your system and we can recommend a suitable desktop or server grade PSU for your requirements. Please get in touch here;  https://www.servercase.co.uk/contact-us/

Tech Help - What wattage PSU do I need for my server?

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