The late 19th century was a period of rapid technological development and innovation. Thomas Edison's incandescent lightbulb, patented in 1879, helped kickstart the era of electrification. However, a major battle soon emerged between Edison's direct current (DC) system and Nikola Tesla's alternating current (AC) system over which was superior for power transmission. This became known as the "War of the Currents." Edison favored DC while Tesla championed AC. In the end, Tesla's AC system triumphed over Edison's DC system due to its ability to transmit electricity efficiently over long distances.

Edison's Direct Current System

Thomas Edison was one of America's most famous inventors and businessmen. In 1879, Edison patented the first commercially viable incandescent lightbulb. To power these new electric lights, Edison developed the first electrical power distribution system using direct current (DC).

In Edison's DC system, electricity flowed in one direction from a generation station along copper wires to the customer. This allowed for electric lighting as the steady uni-directional flow of current could power bulbs connected to the system.

Benefits of Direct Current

Edison's DC system had several key benefits:

Limitations of Direct Current

However, Edison's DC had some major limitations:

Due to these factors, DC systems were impractical for generating and transmitting electricity over long distances such as between cities. The low transmission voltage also meant a power plant needed to be located every mile or so.

Tesla's Alternating Current System

Working under George Westinghouse, Nikola Tesla pioneered the use of alternating current (AC) for electric power systems. In an AC system, the current periodically reverses direction many times per second, often 60 cycles per second (60 Hz) in the U.S.

Advantages of Alternating Current

Tesla's AC had major advantages over Edison's DC:

By using very high voltages, alternating current could be transmitted over long distances with acceptable power loss levels. This allowed large central generating stations to be located far from customers and still provide power economically.

Tesla's Innovations

Tesla made major innovations that allowed practical AC power transmission:

The War of the Currents

The advantages of AC quickly led to competition between the Edison DC system and Tesla/Westinghouse AC system. The "War of the Currents" broke out to determine which system would dominate electrification of America.

Edison's Campaign

Edison launched a propaganda campaign against the dangers of AC power, sponsoring public demonstrations of animals being electrocuted to show AC was deadly:

Triumph of Alternating Current

Despite Edison's efforts, AC proved superior and was rapidly adopted:

Within a decade, AC virtually replaced DC for generation and transmission of power across the country. J.P. Morgan's merger of Edison General Electric and Thomson-Houston created General Electric in 1892, which converted its systems over to AC.


In the "War of the Currents," alternating current defeated direct current due to its ability to transmit power over long distances efficiently. Tesla's innovations like induction motors and transformers enabled AC to be transmitted at high voltage then used at safe low voltages. This allowed the generation and distribution of electricity on a national scale. Though it took years to be convinced, even Edison's company ultimately adopted AC as the superior system.