Introduction to the War of the Currents

The "war of the currents" was a major competition in the late 1880s between Thomas Edison's direct current (DC) system and Nikola Tesla's alternating current (AC) system. Edison had established his Pearl Street Station in New York in 1882, which provided DC electricity using a network of cables buried underground. However, DC systems were limited in how far they could efficiently transmit electricity.

In 1885, Tesla partnered with George Westinghouse to commercialize a new AC system that could transmit electricity over long distances. A war soon erupted between the Edison and Westinghouse camps as they competed to establish their electrical systems across America. Edison viciously attacked and ridiculed AC as unsafe, even going so far as electrocuting animals to demonstrate its dangers. However, despite Edison's aggressive tactics, AC ultimately emerged victorious due to its technical superiority. By the late 1890s, AC was well on its way to becoming the standard for electrical transmission across the United States.

Edison's Push for Direct Current in the Early Days

Thomas Edison was the leading force behind direct current in the early electrical age. In 1879, Edison invented the first practical incandescent light bulb. To capitalize on his new invention, Edison set out to develop an electrical distribution system to provide electricity, using DC current.

At the time, DC offered important advantages:

In 1882, Edison opened Pearl Street Station in New York, the first central power plant in America. It initially powered around 3,000 lamps in lower Manhattan. This demonstrated the viability of electrical lighting on a large scale.

Edison quickly established Edison Illuminating Companies in major cities like New York and Philadelphia. These local franchises installed electric lines, dynamos, fixtures, and lighting to bring electricity to communities. For a period, the future of electricity clearly belonged to Edison and direct current.

Tesla's Breakthrough with Alternating Current

The limitations of DC soon became apparent. Direct current systems were only economical within a radius of approximately one mile from the generating station. This restricted how far electricity could reach consumers.

In 1884, Hungarian engineer Nikola Tesla migrated to America. Unlike Edison, Tesla had a strong background in mathematics and physics. In 1885, Tesla secured funding from investors to develop an AC induction motor, an apparatus that converted electricity into rotary motion. This became Tesla's major technical breakthrough, enabling efficient AC power transmission over long distances.

Tesla shared his idea for a working AC motor with American entrepreneur George Westinghouse. Westinghouse immediately recognized the potential of Tesla's motor for power transmission and obtained patents from Tesla. In 1887, Westinghouse installed the first AC power system, at Great Barrington, MA. This demonstrated the viability of AC for efficient long-range transmission.

Edison's Propaganda Campaign Against AC

Edison fiercely defended his DC advantage and attacked the fledgling AC system as unsafe. To discredit AC, Edison mounted an aggressive propaganda campaign. He spread misinformation that AC could easily electrocute people, referring to alternating current as the "executioner's current."

As part of his campaign against AC, Edison arranged public demonstrations where animals were brutally electrocuted using AC. In 1903, Edison's film company made a movie called Electrocuting an Elephant, showing the killing of an elephant named Topsy at a Coney Island amusement park. This was a misguided attempt to show the public how dangerous AC supposedly was.

Tesla and Westinghouse Promote AC at the 1893 Chicago World's Fair

The key battlefield for AC and DC became the 1893 Chicago World's Fair. Both Westinghouse and Edison bid to illuminate the fair and demonstrate their electrical systems. In a major win for AC, Westinghouse underbid Edison and was awarded the lighting contract.

Westinghouse installed generators at the fair site and lit over 100,000 light bulbs using AC. The dazzling display convinced fairgoers of the enormous potential of AC power. Westinghouse also powered the fair's machinery using AC motors. This wide-scale deployment of AC equipment at the influential Chicago Fair was a major boost for the Tesla/Westinghouse system.

AC Ultimately Wins Due to Its Technical Superiority

Despite Edison's aggressive attacks on AC, the Tesla/Westinghouse alternating current system ultimately emerged victorious as the leading electrical transmission standard. AC offered important technical advantages over DC that led to its dominance:

By the late 1890s, the merits of AC power transmission were simply too great to overlook. The "war of the currents" ended with AC as the reigning standard for long distance electricity transmission, a status it still holds today. This allowed rapid electrification across the country.


The war of the currents between Edison's DC system and Tesla/Westinghouse's AC ultimately resulted in AC's decisive victory. Despite Edison's vicious attacks on AC, its technical advantages for transmitting power over long distances won out. AC enabled nationwide electrification, changing America forever. Today, AC remains the standard for electricity thanks to Tesla's innovations over a century ago.