Can you explain why 50 cps and 60 cps was decided upon?  I would like to know the history of this.   If you don't know, that's fine.  I can probably do some research, but why the differences?  Isn't it time to "best practice" most of the modern world to one simultaneous way of looking at electrical power, one that is most efficient?  Or, is the lesser efficient American way a problem now that over 310+ million people in the USA and another 35+ milllion in Canada use the same 60 cps?,(reply>), +A W 2 Having looked at the Wiki article, I can tell you that history is the reason for this. Back when decisions were being made, many different frequencies (and voltages) were chosen, all involving compromises. Anywhere from 25 Hz to 133 Hz. In general, higher frequencies are better for transformer efficiency (also reduced size) and for lighting users (flicker). For long distance transmission and large electric motor loads, lower frequencies are better. Transmission and distribution loses in the US networks has been measured at about 6.5%.<br><br><br>60Hz is also used in Mexico, Central America and parts of South America. There doesn't seem to be much incentive to change, even though transmission lines are often very long. Americans tend to assume that if change is needed to achieve standardisation, it won't be them that needs to change. You've probably noticed their failure to adopt the metric system. Disclosure, I'm Canadian.