Buying a power supply can be a daunting task as there are many different types to choose from, and they all have their own subtle differences. The power supply unit, or PSU, is the part of a computer that converts alternating current, such as that acquired from almost any wall socket, to low-voltage direct current that can be used by the computer's internal parts. While most power supplies are quite similar and look like a metal box, there are many important differences to be considered while buying a power supply. Different power supplies provide a different amount of power; it is important to be sure that one's power supply provides enough power. Other considerations include the size, shape, efficiency, and running temperature of the power supply.
The most important part of buying a power supply is determining the amount of power needed to run all of the components in a computer. The power supply is responsible for getting the proper amount of power, measured in watts, to different components within the computer. If the power supply cannot provide enough power, the computer will not be able to run properly. While producers of computer parts do try to make computer components as energy efficient as possible, high end processors, graphics cards, and other devices can still drain a significant amount of power. Many suppliers have calculators on the Internet that can analyze the components in a computer and estimate the amount of power needed to run them.
Size and shape are also important considerations when buying a power supply. Many computer components, including power supplies, are built based on the Advanced technology extended, or ATX, form factor. This means that different components can be interchangeably placed in various slots in a computer's case. Before buying a power supply, it is important to determine the form factor of the case. If the case does not support the power supply's form factor, the power supply may not fit at all.
Price is another highly important factor in buying a power supply. The power supply may be one of the least expensive parts of the computer or one of the most, depending on many factors. Power supples that provide more power tend to cost more money, so it is important to ensure that one's power supply meets but does not greatly exceed his power needs. On the other hand, it is important for the power supply to provide at least some extra power; future upgrades may use more energy and power supply efficiency tends to decline over time. Still, there is no need for an expensive 1,000-watt power supply in a system that only draws 500 watts of power.