In electrical power distribution, a busbar (also spelled bus bar, or sometimes as buss bar or bussbar, with the term bus being a contraction of the Latin omnibus, "for all", or buss being short for buttress) is a metallic strip or bar (typically copper, brass or aluminium) that conducts electricity within a switchboard, distribution board, substation, battery bank, or other electrical apparatus. Busbars are used to carry substantial electric currents over relatively short distances; their greater surface area (compared to a wire of the same weight) reduces losses due to corona discharge. Busbars are not normally structural members.
The material composition and cross-sectional size of the busbar determine the maximum amount of current that can be safely carried. Busbars can have a cross-sectional area of as little as 10 square millimetres (0.016 sq in), but electrical substations may use metal tubes 50 millimetres (2.0 in) in diameter (20 square millimetres (0.031 sq in)) or more as busbars. An aluminium smelter will have very large busbars used to carry tens of thousands of amperes to the electrochemical cells that produce aluminium from molten salts.