Best I can find, you can thank Tomas Edison for 120 volt in about 1882. Just happened to work best for the light bulbs he had invented. It appears the Germans get the credit for 230 volt. Reason, thats just the way it was. Countries with 120v say it is safer, 120v to neutral or ground, than Countries with 220v to as high as 240v to neutral or ground. Higher voltage will allow smaller conductor size. Power,watts, equals volts times amps.
I believe in Europe and the United Kingdom they have higher safety standards for their appliances,because of the higher voltage.
I believe in Europe and the United Kingdom they have higher safety standards for their appliances,because of the higher voltage.