Good explanation: nit to pick -- we went to A.C. (original systems were D.C., some remnants existed in NYC and Boston till the mid-2000s) because you can transmit it at high voltage (less loss), then transform it down to a usable voltage at residences or business easily. D.C. would have required rotary converters at the time when the power grid was being built -- you could now do it with solid-state switching and transformers, but it's 100+ years later.