How to Choose the Right Power Supply for your Personal Computer

eiodotcom —  June 6, 2012 — 4 Comments

Power supply units(PSU) are an essential component of any computer: in essence, PSUs provide all the power necessary to your computer by converting AC to low-voltage DC power. Sadly, however, many people do not realize its vast importance to the performance and durability of a computer.

StarTech AT Replacement Power Supply

Combining a shoddy PSU with an expensive computer can cause a variety of problems, such as a power surge damaging expensive computer parts, or crashes and reboots caused by the power level’s failure to support the system. Therefore, selecting the right PSU is essential to having a great personally built computer.

In general, when you are selecting which power supply is best for your needs, there are three main things to think about: 1) a power supply that fits your computer, 2) supplies the correct amount of power, and 3) possesses the correct connectors for your computer’s components.

A Size and Shape that Fits

Power supplies come in a variety of different sizes and shapes called “form factors.” The form factors of the computer case and power supply should match up. If they don’t, the power supply won’t fit.

In general, there are two main types of form factors for computer cases: the ATX (Advanced Technology Extended) and BTX (Balanced Technology Extended). The mid-size ATX is the most common size of computer case and will fit most power supplies. But be careful, because there is a full ATX which houses a much larger motherboard, and will be enormous compared to a mid-ATX sized power supply.

An Appropriate Amount of Power

The next step in determining the correct power supply is to figure out the appropriate amount of power your computer needs. According to, power supplies have two different wattages to pay attention to: true wattage and max wattage. “Max wattage shows the maximum power that particular unit can supply and it is almost never reached during every day use. True wattage shows the actual wattage which the PSU will supply most of the time.”

The Information for Voltage and Current Levels

Thus, it is more important to know the true wattage of the computer over the max wattage.

Furthermore, the amount of power a computer needs is based on the internal components and how much power they use. Computers will use and need more power if they house high-end graphics cards, powerful processors/motherboards, and multiple disk drives.

As a rule of thumb, its always better to buy a power supply with 50W-100W over the recommended power needed, so you can always expand your computer’s capabilities later. You never want to buy a power supply and then later realize it won’t suit the future additions you might add on. This PSU calculator is a good guide to determine how much power you’ll need.

The Correct Connectors

Another important factor in selecting a suitable power supply is to choose a power supply with the proper number and types of connectors. There are different molex and SATA connectors. Motherboards, processors, and PCI expansion cords all come with various types of connectors, so be sure all those parts line up with the power supply you choose. You can go the route of obtaining adapters, but remember not to have too many cords or adapters in your computer, which can impede the air flow within the computer tower and thus overheat your power supply.

The Variety of Power Supply Connectors

Other Things to Think About

Finally, there are a few other important things to think about when selecting the right power supply. I’ll only briefly mention these here:

  • Energy efficiency
  • Cooling fan – type, as well as how much noise it makes
  • Brand name CPUs vs. generic power supplies

Here are some of Eio‘s more popular computer power supplies:

Athena Power AP-MFATX25P8 20+4Pin 250W Single 80 PLUS Certified Server Power Supply

APEVIA ATX-JV650W 650W ATX12V/EPS12V SLI Ready CrossFire Ready Power Supply

See also:


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