The "standard" power line frequency back in the early days of hydroelectricity generation at Niagara Falls was 25 cycles per second (Hz). I had an electronics t

The "standard" power line frequency back in the early days of hydroelectricity generation at Niagara Falls was 25 cycles per second (Hz). I had an electronics teacher who used to tell us how the power companies of Upstate New York and Southern Ontario made the transition to 60Hz very abruptly, with crews going door-to-door exchanging any appliance or equipment wired for 25Hz for an equivalent, brand new 60Hz model. Bear in mind that this predated almost all electronic devices. 25Hz generation carried on at several Niagara sites well into the late 20th century, although by then any 25Hz generator would have been paired with a frequency shifter as needed, which was simply a 25Hz motor geared to a 60Hz generator. Yes, there were energy losses inherent in such a system, but all the engineers had to do was point at Niagara Falls and say "No worries, there's plenty of energy here."