Uninterruptible power supply

An uninterruptible power supply, usually shortened to UPS, is a power protection device or system that uses stored energy to keep a connected load running when the normal mains supply fails or falls outside acceptable limits. It is commonly used for IT equipment, controls and other loads that need short-term continuity rather than a normal shutdown as soon as grid power is lost. In home energy contexts, the term matters because a battery system, EPS output or island-mode arrangement is not automatically a UPS. A home battery may provide backup power to a socket, selected circuits or a wider backup arrangement, but the continuity depends on the product's transfer time, inverter output, battery state of charge, circuit design and protection arrangement.