Power Management is a feature of some electrical appliances, especially copiers, computers, GPUs and computer peripherals such as monitors and printers, that turns off the power or switches the system to a low-power state when inactive. In computing this is known as PC power management and is built around a standard called ACPI. This supersedesAPM. All recent (consumer) computers have ACPI support.
In the military, ""Power Management"" often refers to suites of equipment which permit soldiers and squads to share diverse energy sources, powering often incompatible equipment.