How Do I Choose the Best Computer Power Supply?

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  • Written By: Robert Grimmick
  • Edited By: R. Halprin
  • Last Modified Date: 17 March 2014
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Choosing the best computer power supply is generally an individualized experience. There is no single power supply that is perfect for everyone. There are, however, several factors that you may want to take into consideration. For example, you’ll want to choose a power supply that fits your computer, supplies an appropriate amount of power, and has the right connectors for your computer’s components.

A computer power supply converts the alternating current (AC) from a wall plug into direct current (DC) needed to power the components inside a computer. It also steps down the voltage to a level appropriate for those components. Heat is generated during this conversion process, so most power supplies have fans to keep them cool. Silent, fan-less models are also available.

Power supplies come in a variety of different sizes and shapes called "form factors." Make sure the form factor of your computer power supply matches that of your computer’s case; otherwise it will not fit. One of the most common types is the Advanced Technology Extended (ATX) form factor used in many desktop computers.

A computer power supply is rated in watts according to its maximum possible power output. The amount of power a computer needs is based on its internal components. High-end graphics cards, powerful processors, and multiple disk drives will make a computer power-hungry.


Manufactures test their power supplies under different conditions, which can affect the rating. Cheap or generic power supplies have ratings that can be very inaccurate. It’s generally a good idea to buy a computer power supply with a rating slightly higher than what you’ll need. Power supplies are most efficient at higher loads, so buying one with a rating much higher than you need can waste electricity.

Another important factor is a computer power supply with the proper number and types of connectors for your requirements. Different motherboards, processors, and expansion cards have different types of connectors. Some devices are also modular, meaning different types of connectors can be attached to or removed from a power supply depending on your needs.

A rating known as the mean time between failures (MTBF) can help you choose a more reliable computer power supply. In general, higher MBTF ratings are a sign of higher quality. A poor quality power supply can shorten the life of computer components.

If energy efficiency is important to you, consider a computer power supply with an 80 PLUS® certification. When power is converted from AC to DC, some energy is lost as heat. 80 PLUS® certified products lose 20% or less energy during the conversion under standard operating conditions, saving electricity.


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