One essential part of a computer system is the PC power supply, sometimes referred to as the PSU (Power Supply Unit). A PC power supply's main job is to supply all of the components of a computer?the motherboard, CPU, graphics card, storage devices, and peripherals?with the electrical energy they require. When the computer's components need DC (direct current) power, it transforms AC (alternating current) power from a wall socket. Important Power Supply Features: Rating of Wattage: The PSU's maximum power output is indicated by the wattage rating. Selecting a power supply that can support the demands of the CPU, graphics card, and peripherals in a computer requires a certain wattage. Rating of Efficiency