The ACUPWR Papers

An Explanation Why Different International Voltage Standards and Plug Shapes Exist

Variety is the spice of life, a notion perfectly applicable to international travel. Why travel at all if not to see, hear, and experience the culture, cuisine, language and weird police car sirens that let you know you’re far from home. Add different voltage standards and plug shapes to those unique identifiers that make Brazil Brazil, or New Zealand New Zealand

Traveling would be easier if all voltage standards were uniform the world over; there would be no anxiety about combustible hairdryers and no nightmare tales of plugging in a 110/120V appliance into a 220/240V outlet with a fireworks display. And having one standard plug shape would certainly eliminate the need for plug adapters. Yet because there’s no such standard, it’s the reason ACUPWR’s in business. Still, it begs the question why different voltage standards exist. How did they originate and why?

On the surface, voltage standards and odd plug shapes might seem like a particular country’s reflection of individuality and culture, much like currency, the national bird, or a flag.   

The variation of plug types are pretty much dictated by national standards and individuality. Israel’s type H shape is unique to that country. Australia and New Zealand use the recognizable type I shape, which originated in Australia and spread to New Zealand and eventually Argentina. South Africa uses its own, distinctively oversized type M plug. Why? Because they can. The UK uses a fuse-equipped type G plug (the BS 1363) mandated by law to prevent fire hazards. In the end it’s about national standards.

As for voltage and AC line frequency, the rates are based on a combination of safety and efficiency. The United States chose 110-120 volts for safety and the 60 Hz frequency standard was chosen by Nikola Tesla, the inventor of AC and too many other things to mention, based on his calculations for efficiency. Germany’s AEG electricity company established 50 Hz (as that number fits their metric standard) and originally 110-120 volts but later 220-240 volts because the latter was deemed more effective for long-distance power transmission. For Mexico and Brazil, the voltage standard is 127-130 volts and 60 Hz, chosen for safety, while Japan’s 100 volts and 50 or 60 Hz standard—depending where in Japan you are—was established more than 125 years ago, for safety concerns. It’s been in place solidly over the years, through periods of war and economic rise and collapse, and it isn’t changing anytime soon.  

In the past, the International Electricity Commision, or IEC, which was organized back in 1906 to establish standards, has attempted to create a universal plug type. In the end it was a case of “if it ain’t broke…” National standards for plug types, AC frequency, and voltage are too well entrenched to change at this point in the electrical age. Actually, it’s now the digital age and there are other standards to worry about.

For a complete list of international voltage standards and accompanying plug types, visit

For a complete list of plug shapes, their corresponding type letter, and countries of use, visit ACUPWR’s plug adapter page

And remember to use ACUPWR voltage transformers and converters so you can see the world and stay plugged in—safely!

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