How to choose the best PSU (Power Supply Unit) for the money


PSU Power Supply

Buying a power supply can be a daunting task for many PC builders, the prices and rated capabilities range widely and there is little in comparable specifications. To make matters worse the power supply doesn’t affect performance in any direct way. Buying a $200 dollar power supply won’t make your computer run any faster compared to a $50 dollar supply, this leaves people with the unfortunate task of trying to not spend more money than they need to, as this money could be better spent on other components, but at the same time not buying a power supply that will underperform.

Brand is Key

I know it’s weird to forget the specs and make a decision based on brand, but when it comes to power supplies, build quality is extremely important. Power supplies heat up from constant use and this is the last thing you want to die while using your computer. Because the power supply is connected to every component in your computer, it has the potential to fry any or all of them if it were to fail. This makes having a top quality supply, that uses good quality parts combined with an efficient airflow, an extremely important when picking the correct one for you. By picking a name brand you are more likely to have one that will work under stress and won’t die due to overheating or not being able to supply enough electricity. Below is a few notable brands, while by no means exhaustive, gives you an idea of who is generally considered a reliable brand:

  • Thermaltake
  • Corsair
  • PC Power and Cooling
  • Antec


The main problem most consumers have when picking the right power supply is how can I figure out if Brand A’s 500 watts is the same as Brand B’s. This is difficult as most companies rate their own power supplies and rate them at the maximum wattage. The maximum wattage rating is there to let you know the max amount of electricity that can go through the power supply before it blows, this does not mean that you will ever be able reach that level under normal use or before it would fail. This is extremely misleading as to what most no name brands use to make their power supplies seem comparable to the more expensive name brand ones. One way to figure out if a power supply can perform as advertised is to calculate the continuous output the power supply has. The equation to figure out the continuous output is to multiply the 12 volt rails by their amperage. This cheap power supply from newegg is rated at 500watts, this being maximum output:

This Linkworld power supply has a +12 volt rail of 20 Amps, making its continuous output a mere 240 Watts, more than half of its advertised performance. This means that if you were lucky you might get up to 300 Watts before the supply failed on you. This more expensive Thermaltake 500 watt power supply has (2) 12 volt rails, these 2 rails is used as a safety feature to spread the power and are calculated separately and added together.

This power supply has 1 12 volt rail at 25 and the other at 18 giving it a combined continuous output of 516, effectively doubling the power compared to the other 500 watts PSU.

You may have noticed that there are other output levels, these can be ignored for the most part as the 3.3v and the 5v deal with the circuitry, while the 12v deals with the power supply and moving parts of the computer like the hard drives, fans and graphics card. 

Continue to Part 2

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About The Author

President of NSI, Tom has been helping small and medium businesses succeed in Connecticut for over 25 years.