A Power Supply Unit (PSU) is a hardware component of a computer that supplies all other components with power. It converts mains AC to low-voltage regulated DC power for the internal components of a computer). Modern personal computers universally use switched-mode power supplies (SMPS), which have both efficiency advantages and make designing for multiple voltage inputs easier. The most recent ATX PSU standard is version 3.0 as of mid-2022).

The PSU provides power to the motherboard, processor, and peripheral devices). Several direct-current voltages are required, and they must be regulated with some accuracy to provide stable operation of the computer). The power rating of a PSU describes the total system power that can be drawn from the unit before it overloads, usually expressed as Watts (W) . Modern PSUs commonly range from 300W to over 1000W.

It is important to choose the right PSU for your system, and the latest 80 Plus PSUs require high wattage to run most effectively. The 80 Plus Gold, Platinum, and Titanium supplies (up to 94%) are ideal for large data centers, while 80 Plus Silver power supplies and below (a maximum efficiency of 88%) are more suitable for PCs and desktops.