<P> The War of Currents (sometimes called War of the Currents or Battle of Currents) was a format war involving the introduction of competing electric power transmission systems in the late 1880s and early 1890s . It included commercial competition, a debate over electrical safety, and a media / propaganda campaign that grew out of it, with the main players being the direct current (DC) based Edison Electric Light Company and the alternating current (AC) based Westinghouse Electric Company . It took place during the introduction and rapid expansion of the alternating current standard (already in use and advocated by several US and European companies) and its eventual adoption over the direct current distribution system . Three aspects have been conflated into the "war": open competition involving large electric companies and their developing systems, a general fear in the public's mind of death by accidental electrocution from high voltage AC leading to a debate over its safety and regulation, and the debate and behind - the - scene maneuvers associated with the introduction of the electric chair . </P> <P> The introduction of large scale outdoor arc lighting systems in the mid to late 1870s, some of them powered by high - voltage alternating current, was followed in 1882 by Thomas Edison's low voltage DC electric distribution "utility" designed for indoor business and residential use as an alternative to gas and oil - based lighting . In 1886 George Westinghouse began building an alternating current system that used a transformer to step up voltage for long - distance transmission and then stepped it back down for indoor lighting, a more efficient and less expensive system that directly competed for the market the Edison system was designed to serve . As many other electric companies joined in and the use of AC spread rapidly, Edison's company made claims in early 1888 that alternating current was hazardous and inferior to the patented direct current system . </P>

Who discovered the advantages of ac over dc