Prior to Edison s central power station, each user of electricity needed a dynamo , which was inconvenient and expensive. Edison opened the first commercial electric station in London in 1882; in September the Pearl Street Station in New York City marked the beginning of America s electrical age. Within 4 months the station was lighting more than 5,000 lamps for 230 customers, and the demand for lamps exceeded supply. By 1890 it supplied current to 20,000 lamps, mainly in office buildings, and to motors, fans, printing presses, and heating appliances. Many towns and cities installed central stations. Increased use of electricity led to Edison-base sockets, junction boxes, safety fuses, underground conduits, meters, and the three-wire system. Jumbo dynamos, with drum-wound armatures, could maintain 110 volts with 90 percent efficiency. The three-wire system, first installed in Sunbury, Pennsylvania, in 1883, superseded the parallel circuit, used 110 volts, and necessitated high-resistance lamp filaments .

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