Why are there differences in the use of 110V and 220V voltages between countries in the world?

Tram Ho

Our electrical and electronic devices in Vietnam market are often used at 220V voltage. However, there will be times when you encounter items originating from the US or Japan that require the use of 110V voltage and for use at the grid in Vietnam, we need to have the voltage converter from 220V down. 110V. In addition, for some of you who often go abroad, you will probably be familiar with the difference in voltage of the national grid between countries.

So what is the cause of this difference? Let’s find the answer through this article: Why are there differences in voltage standards between countries?

The situation of using voltage between countries in the world

As you can see in the map above, the standard for alternating electricity use varies from country to world. Normally, 220-240V voltage is most widely used with most countries including Europe, many Asian countries, Africa and of course Vietnam. Next is the 100-127V voltage that is widely used in the entire North American territory, some South American countries, Japan and Taiwan.

In addition, another parameter is also worth noting is the frequency of alternating current (abbreviated as AC, unit of measurement is Hz). Most countries use alternating current with a frequency of 50Hz. A few others use 60Hz frequency. US grid standards in particular are 120V and 60Hz. However, the actual average voltage in the US is around 117V. This is different from many other parts of the world, which mostly use voltage from 220 to 240V.

The question here is:

  • How are the voltage and frequency parameters selected?
  • Are there any exceptions?

We will answer these questions in turn. First of all, everything begins with the electric war between two genius inventors: Nicolas Tesla and Thomas Edison. But first, let’s find out the basic differences between 110V and 220V voltages.

The difference between 110V and 220V voltage

The first thing to say here is that both voltages are potentially dangerous to human life. However, the higher the voltage, the greater the danger. As we know one of the effects of electric current is the physiological effect. According to the study, 24V voltage and 10mA or more current can cause death. Therefore, be very careful when using electricity no matter what voltage it is.

Theoretically , the concept of voltage or voltage is the difference in voltage between two points. The potential difference is that it is possible to move a charge particle in an electrostatic field from one point to another. In the international measurement system, the unit of voltage is Volt (abbreviated as V). The greater the voltage, the stronger the repulsive force of charged particles. It is understandable that if comparing the current as a water flow, the voltage is the flowing force of the water flow. The higher the water level difference between the two points, the stronger the water flow.

In terms of used equipment , the manufacturer fabricates devices suitable for each voltage standard used in different places. Mainly 100-120V and 220-240V. Some small capacity vehicles are usually produced in both 110 and 220V voltages. High capacity devices such as dryers, compressors, etc. often require the use of 220V voltage.

About the wiring aspect . Basically, alternating current (AC) is divided into 1-phase and 3-phase circuits. An AC single-phase circuit has two wires connected to the power source. However, unlike the one-way circuit (DC) whose direction of current does not change, the direction of the current in the AC circuit changes many times per second depending on the frequency (here we are talking about 50Hz ) of the power source in the circuit. 220V power supplied to each household used is 1-phase AC and has 2 wires: phase and neutral wires (hot wires and cold wires).

However, the power distribution line that you often see outside may have four wires. 3 electrical wires (phase wires) and the same neutral wire (cold wire). The three-phase system has three waveforms, 2/3 pi radian (120 degrees, 1/3 cycles), which are different in time.

In terms of economic efficiency , 110-120V voltage is said to be safer but there is a more expensive distribution network due to its capacity, which requires a larger wire section, so the cost of processing materials creating wires will be bigger. In addition to avoiding net loss caused by pure resistors, conductors that need to use purer materials should be more expensive (use less copper to phase). In contrast, 240V power is easier to transmit, higher efficiency and lower loss but less secure.

In the beginning, most countries used 110V voltage. Then due to increased demand, it is necessary to replace wires to withstand higher currents. At that time, some countries went to use double voltage, ie 220V. The smaller the electrical system, the younger the conversion will not be high and vice versa.

In terms of macroeconomics, voltage is also a tool to regulate national trade, avoiding cheap goods from this country overflowing to other countries.

The choice of which type of voltage to use across the country is based not only on technical factors but also on other factors such as grid scale, historical and political contexts, etc.

History of voltage and frequency – It all started from a war and …

The current three-phase alternating electrical system includes the creation, transmission and supply that has been developed since the 19th century with the work of great inventors Nikola Tesla, George Westinghouse and others. Thomas Edison developed a one-way (DC) electrical system with 110V voltage and stated that this system is safe compared to alternating current. This is Edison’s argument in the battle between advocates of AC and DC: AC vs DC War (War of Current)

Thomas Edison’s one-way grid

Image of inventor Thomas Edison (1847-1931)

At the beginning of the electrical system, one-way electric model of Thomas Edison was used in the US with 110V voltage. 110V DC power system is provided by Edison’s General Electric Company throughout the United States for his own invention. However, the one-way electricity system soon reveals its disadvantages that it cannot be applied on a large scale to make a giant national grid.

Tesla proposed AC power system

Inventor, physicist, mechanical engineer and electronic engineer Nikola Tesla (1856-1943)

After that, the electricity grid provides households and businesses in the US quickly converted to AC. This is a 3-phase AC system developed by Nilola Tesla with a voltage of 240 V. It is a system of three alternating currents with the same amplitude, the same frequency, but deviated in time by 1/3. cycle. The three-phase line has the advantages that a single-phase line cannot have. Tesla has calculated that 60 cycles per second or current with 60Hz frequency is the highest efficiency. However, for safety reasons, Tesla finally reduced the voltage to 120V in accordance with the devices designed to operate under low voltage.

Europe switched to 50hz current frequency

After filament bulbs are widely available. In 1899, thanks to the ability of the filament bulbs to withstand the high voltage of the time, the Berlin electric company Berliner Elektrizitäts-Werke (BEW) decided to increase its power distribution by switch to apply 220V rated voltage. As a result, the company used the cost of converting customers’ equipment to compensate for the cost of upgrading the power line. This became the electricity distribution model selected by many power companies in Germany and Europe. This makes the 220V power system popular throughout Europe.

Picture of a factory of Berliner Elektrizitäts-Werke electric company

With the support of Westinghouse, Tesla’s AC system became standard in the United States. Meanwhile, AEG company in Germany began to produce and invisiblely monopolize the power supply market in Europe. They decided to use the current with 50Hz frequency instead of 60hz to match the standard measurement system of metric (metric) here.

Unfortunately, alternating current of 50Hz has a large loss, but the efficiency is not as high as 60Hz. The reason is that 50Hz generators are 20% lower than 60Hz generators. Consequently, the transmission of current at a frequency of 50Hz is 10 to 15% less efficient. In addition, 50Hz transformers require larger coils and 50Hz electric motors operate less efficiently than 60Hz. All of these factors affect the loss of electrical energy and create more useless heat at low frequencies.

Europe switched to 230V voltage

Europe continued to maintain AC 120V until the 1950s. After World War II, Europe switched to using 230V electricity to improve the efficiency of electricity transmission in the grid. The UK not only switched to 230V voltage but also switched from 60Hz to 50Hz. The cause of all of Europe can easily change the main electricity standard is due in part to the aftermath of the Second World War. are all badly destroyed. This allows the construction of an entirely new standard electrical system without a lot of money.

The United States remains the original AC system: 120V, 60Hz

For many years, the United States has repeatedly considered switching to 220V power system to apply to households across the country. However, this needs to cost a huge amount to be able to rebuild the national electricity network. At the same time, all devices designed using 120V voltage have to be replaced completely. This is an almost impossible thing. One disadvantage of the US power system is that there is not enough voltage at the end of the line.

However, in an effort to replace the voltage standard to 240V, a compromise was built in the US to provide 240V voltage. Accordingly, the supply voltage to each family will be 240V. It will then be lowered to 120V to use old appliances. Some new household appliances such as electric stoves or clothes dryers in the US will be designed to use a maximum voltage of 240V.

So we understand the difference between electrical systems in the largest regions in the world. The difference between standard 110-120V voltage in the US and 230V in Europe is mainly historical factors. The choice of different voltages in each major area originates from the first and the first electric sessions invented to everyone. The reason Europe can switch to 230V power system is also thanks to the consequences of World War II.

On the other hand, in terms of history, Europe has a great influence on the rest of the world in terms of science and technology in general and the electricity sector in particular. Therefore, many other places in the world are influenced by the 220-240V voltage standard depending on the conditions and historical context of each country.

Some exceptions – Where the standard voltage cannot be determined

Image of hydroelectric dam in Brazil

In Brazil, many places mainly use voltage from 110V to 127V. However, some hotels use 220V voltage. Brasilia and northeastern Brazil use 220-240V voltage.

In Japan, one uses the same voltage standard for all places but with different frequencies between regions. East Japan including Tokyo uses 50Hz frequency. Western Japan including Osaka and Kyoto uses 60Hz frequency.

Map of power companies in Japan and the difference in frequency of current between east and west

The main reason is that after World War II, Britain was responsible for helping to reconstruct the electric system in eastern Japan. The US is also responsible for rebuilding the electricity system in the western region of the country. It is worth mentioning here that after the war, Britain and all European countries switched to using 240V voltage and 50Hz frequency, but the British built 100-110V power system with 50Hz frequency in Japan.

The inconsistency in the frequency of electricity has caused many difficulties for Japanese people as well as tourists coming here when it is easy to confuse the use of electrical equipment. At the same time, this also creates a cost when using more current switching devices or making it difficult to choose to buy equipment.


AC voltage and frequency vary widely between countries around the world. Many places use 230V voltage and 50Hz frequency. About 20% of the world’s countries use 110V voltage and / or 60Hz frequency for household electrical systems. 240V voltage and 60Hz frequency have the most effective use but only some countries choose to use it.

Hopefully, through the article, you can partly explain the cause of this difference in voltage used. Not only based on simple technical factors but also on the historical, political and cultural situation in different countries or regions.

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Source : tinhte.vn