Anecdotally, I have been told that the reason each home in the US has its own transformer is due to the problems of distribution. If the 120 volts was carried distances over power lines voltage drop would be an issue. By transforming the high voltage at each home this problem is minimised.
It is not true that each home in the US has its own transformer.
I have lived in numerous areas, and I am quite sure that in every one there has been a transformer for a group of homes. I haven't bothered counting homes per transformer, but it certainly is more like 10:1 or 20:1 than 1:1.
I *know* that in my current home there is one transformer for about 20 homes, because it is an old system (about 60 years old), and we have problems with overloading when everyone on the block turns on their air conditioner.
Electrical Engineer
Industrial manufacturing manager
Salt Lake City, Utah, USA
www.qsicorp.com
