A bus, or bus bar, is a conductor, often a heavy strap or bar, used to establish a common connection between multiple electrical circuits.
In electrical distribution systems, a bus bar acts as a centralized point where current is collected and distributed to various circuits or loads. Constructed from highly conductive metals such as copper or aluminum, bus bars are designed to carry large amounts of current with minimal energy loss. Their rigid, durable form ensures efficient current flow, making them essential in switchgear, panelboards, substations, and other infrastructure. Bus bars simplify layouts by replacing multiple smaller conductors, reducing resistance, and enabling compact designs. Depending on the application, they may be flat, solid, hollow, or laminated, and can include insulation or protective coatings for added safety.
Bus bars are subject to standards from the NEC (National Electrical Code), UL (Underwriters Laboratories), IEEE (Institute of Electrical and Electronics Engineers), and IEC (International Electrotechnical Commission).
Bus bars became common in the late 19th and early 20th centuries as centralized power distribution systems emerged. Industrial facilities and utilities required higher-capacity conductors, and rigid bus bars provided greater efficiency and reliability than bundled wires. Modern designs now include insulated, coated, and modular bus bar systems to meet evolving demands.