When It Comes to Voltage, It’s All About the History – and the Money

We take electric power for granted. That becomes painfully obvious when there’s a power failure (Stromausfall). In total darkness, carrying a flashlight, we absentmindedly try to switch on the light. Duh!

Expats and international travelers know that the electric power in Europe is different from the power in North America. No surprise there. But why? Why does most of the world use double the voltage that comes out of an American power outlet? And why does European alternating current (AC) operate at 50 cycles per second (50 hertz, 50Hz), but AC in North America (including Mexico) is 60 hertz? Is one better than the other? How did this happen?

If you look around the globe, you’ll find a wide variety of electric power voltages. Japan for some reason has 100 volts, the lowest household power voltage in the world. (And half the country is 50Hz, the other 60Hz, apparently the result of German versus US equipment back in the 1890s.) Europe’s power grid, the world’s most interconnected, is set at 230 volts (an EU standard since 2008). The United States power grid is much less well integrated, but all over North America the voltage is a nominal 120 volts. (Actual voltage at the wall outlet or light switch in any system can vary by plus or minus 5 to 10 percent.) By far most of the world uses 220-240 volts. Of course, all over the world power poles or underground lines transmit power at much higher voltages. That power is stepped down by transformers before the power enters a building’s main electric panel.

This color-coded map showing various electrical plug types used around the world. Although all of Europe is 230 volts and 50Hz, the same can’t be said for electrical plugs and sockets. IMAGE: Wikimedia Commons

In reality the US and Canada also have 200+ volts, to be specific, 240-volt power. The electric power coming into a North American home or business is actually 240 volts, which is then split into two 120-volt lines (normally a split-phase three-wire system). The 120-volt outlets are for lighting, small appliances, and other devices (TV set, computer, toaster, etc.). The oven, cooking range, air conditioner, electric water heater, EV charger, and other high-power devices use the full 240 volts, using special grounded plugs and outlets that are larger than the 120-volt type. (It’s a little more technical than that, but for our purposes this should suffice.) In Europe the normal power outlets are 230 volts and the high-power appliances are fed 400 volts (formerly 380 volts).

But Why? Warum?
But why, you ask, is there a 120-volt standard in North America and a 230-volt one in Europe? The exact reasons are not certain, but there are a few good candidates. The first answer, and the one most people cite, is Thomas Edison. Although he was not the first person to invent the light bulb, Edison is remembered as the inventor because he did not just invent the incandescent light bulb, he invented a superior one. And he also invented an entire system to make his light bulb work. In a way, you could say the light bulb wasn’t the most important thing. It was just part of a power package: generator, main feeder, distribution lines, house wiring, and the light bulbs.

That was Edison’s genius: “Not only do I have a light bulb, I offer you an entire system to light it up.” He worked hard to come up with the right filament that would burn for hundreds of hours. And what voltage worked best with his light bulb? 110 volts was the magic number. All of Edison’s power installations across the United States were 110 volts DC. (It was the DC part that was Edison’s downfall. Direct current can’t travel long distances. George Westinghouse and others went with alternating current, and won the “war of currents.”)

Answer two may or may not be true, but some people promote it. (Or maybe the two answers actually go together.) Arc light came before incandescent light. It was too bright and dangerous to use indoors, but it was used for a while in some cities outdoors. A standard arc light operated at 50 or 55 volts. But that voltage was too low to be efficient. Usually two arc lamps were used in series, meaning a voltage of 100 or 110 volts. So 100 or 110 volts became a norm even before the light bulb showed up. In 1892 Germany’s first long-distance AC transmission line between Lauffen and Frankfurt (see below) carried 55-volt 40Hz AC power. (The AC cycle rate varied a lot in the early days of AC power, varying from 40 to 133 hertz, before 50Hz and 60Hz became the standards used today.)

But why are there still two different main voltage standards (100-120V and 220-240V) in the world? Read on.

From 100 to 240 Volts Around the Globe

As we saw with Japan’s 100-volt 50Hz/60Hz system above, that oddity goes back to the past when two competing firms from different countries used two different technical standards. The reason it hasn’t changed since 1890, is the same reason North America still has 120-volt power and Europe has 230 volts: Making the change – replacing older appliances, light bulbs, wiring, transformers, and generators – would have created great costs and difficulty. The US, which started with 110-volt power, actually considered switching to more-efficient 220-volt household power in the 1950s. Europe had developed its 220-volt (now 230-volt) system after learning from the American experience, and before any massive infrastructure changes would be required. But some parts of Europe were originally 120 volts also.

A typical German/European “Schuko” plug and socket (Type F). The top and bottom metal contacts are the ground. PHOTO: Wikimedia Commons

Europe

The world’s first large scale central power plant was the Edison Electric Light Company’s steam powered station at Holborn Viaduct in London, which began operation in January 1882. Holburn produced 110-volt direct current. The London station served as a model for the construction of the much larger Pearl Street Station in Manhattan, the world’s first permanent commercial central power plant. But Edison’s direct current was losing the AC vs DC battle to Nicola Tesla’s alternating current. The future would belong to AC.

It was the Germans who introduced AC power in Europe. The 1891 International Electro-Technical Exhibition in Germany would prove to be a key event in the development of electric power. The exhibition featured a hydroelectric power station at Lauffen, with transmission lines that extended 109 miles (176 km) north to Frankfurt am Main. The Lauffen-Frankfurt line was the first efficient long-distance transmission system. Planned and installed by the German AEG company, the project demonstrated the superiority of Mikhail Osipovich Dolivo-Dobrovolsky’s three-phase AC system over Edison’s DC and Tesla’s two-phase AC systems. It transmitted 55-volt 40Hz AC power. (Russian-born Dolivo-Dobrovolsky [1862-1919] immigrated to Germany to study electrical engineering in Darmstadt. He later worked in Berlin and Lausanne, and did important work in electrical science and obtained over 60 patents. His grave is in Darmstadt.) Emil Rathenau’s AEG (Allgemeine Electricitätsgesellschaft) became a leader in AC technology, putting it ahead of Siemens and Edison, and that was big factor in making AEG a global firm. AEG was the new name of the German Edison Company.

230-Volt 50Hz AC Power
It was around 1893 when the AC frequencies were standardized at 60Hz (US) and 50Hz (Europe). The American Westinghouse Electric Company and Germany’s AEG set their generation equipment to function at 60Hz and 50Hz respectively, leading the way for what would become the world’s two standard AC frequencies. Today most 60Hz systems deliver nominal 120/240 volts, and most 50Hz nominally 230 volts.

No matter the voltage, 60Hz is more efficient than 50Hz, a fact established by Tesla’s pioneering work. (He also preferred 240-volt power.) 50Hz power is 20 percent less effective in generation, and it is 10-15 percent less efficient in transmission. Electric motors are also much less efficient at the lower frequency. Today only a handful of countries (Antigua, Guyana, Peru, the Philippines, South Korea and some others) follow Tesla’s advice and use the 60 Hz frequency together with a voltage of 220-240 V.

Cost was the main reason Europe went with 220 volts (now 230). Counterintuitively, higher voltages allow the use of thinner wire, meaning less copper in the early days of power lines. Power companies could save money on wire by using 220 volts rather than 110. Berlin is one example.

Berlin
In 1899 the Berliner Elektrizitäts-Werke (BEW), a Berlin electrical utility, decided to greatly increase its distribution capacity by switching to 220-volt nominal distribution, taking advantage of the higher voltage capability of newly developed metal filament lamps. The company was able to offset the cost of converting the customer’s equipment by the resulting savings in thinner copper transmission lines. This became the model for electrical distribution in Germany and the rest of Europe and the 220-volt system (later 230-volt) soon became the European norm.

BEW later became Bewag, which in 2005 was swallowed by Vattenfall Europe Berlin AG.

– HF