What is a PSU?

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What is a "PSU"?

A "PSU" or "Power Supply Unit" is a component within a system that allows your PC to receive power. Without it, your system would not be able to turn on. An example of a PSU is shown below.

How does a PSU work?

First, we need to point out that a Power Supply Unit does not supply power but instead converts AC power (power that comes from a wall outlet) to DC power. Power needs to be converted for your PC due to the excellent tolerances in voltage a computer needs to operate. So let's get into the fundamental concepts of a PSU. 


Regarding PC use, wattage is the quantified amount of power that a PSU can supply to your PC. Therefore, a PSU will be able to output the amount of power that it is listed for. Typical wattages for a power supply can usually be 650W, 750W, 850W, and 1000W.


Efficiency Ratings:

Efficiency ratings are used to determine how much power it takes for the PSU to pull from your wall outlet to create the listed output wattage. The best standard for efficiency is the 80 Plus standard, and how efficient your PSU is will be indicated by whether it's listed as Bronze, Silver, Gold, Platinum, or Titanium. Efficiency does not affect the total power a PSU can output to your PC, as no matter what, your PSU will always be able to output to what it is rated for.

Remember how a PSU's job is to convert AC to DC power? When you convert power, you will lose some of it as dispersed heat in the conversion process. Efficiency is how much power has to be pulled from your outlet to hit the output wattage your PSU is rated for to your computer.

For example, if your PSU were a 650W 80 plus bronze, to output 650W of power, your PSU would pull (at an efficiency of 82%) 767W of power to achieve that. That is a lot of technical information, so the short answer to efficiency is that a higher standard will cost less to operate monthly.

What is PSU Efficiency and Why is it Important? | Velocity Micro Blog

So what PSU do I get?

Choosing a PSU is effortless because our site will automatically calculate the total power draw of your PC and determine the best PSU for your build. So you do not need to select anything at all! Often customers will ask, "What if I want a PSU that is future proof? Would I need to pick a different PSU for that?" Just keep in mind that it's pretty uncommon for new components that come out to have significantly higher wattage draws. If you want to be prepared, we recommend an 850W or more Gold PSU; otherwise, let our configurator select the best PSU we have available for your PC.

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