The alternating current for the purpose of supplying private housholds goes back to Nicola Tesla. George Westinghouse acquired the Tesla patents and managed to get the edge on his colleague Thomas Edison with his direct current model. Today AC is the standard.
By the time it arrives at the wall socket and can be conveniently „tapped“, it usually has already travelled several kilometres. The electricity that is converted in power plants from heat and movement, can only be transported over such long distances with reasonable amounts of losses in the form of high voltage. Only alternating currents – and this was the reason for Edison‘s defeat – can be transformed into high voltage. Closer to the consumer, it is gradually transformed down from up to 380,000 volts in the transmission lines until it reaches households with 230 volts (3 x phase-shifted by 120° to each other) or as three-phase current with 400 volts