115 Volts or 220 Volts ?

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.

Before we give Mr Edison too much credit for any AC current distribution, see below

http://www.teslasociety.com/ac.htm

Audioak

I didn`t give Edison credit for ac current!You did! I Just said Tomas Edison found that 120
volt nominal voltage worked for his light bulbs! And thats where it aparently started.