"Don Pearce" wrote in message
...

Do the 120V and 240V system share the same high voltage distribution
lines? I mean is the transformation done per house, per street or per
district?

It is done as needed. In a residential neighborhood there may be several
transformers per block. There is a transformer in my back yard and I can
see the next one maybe 6-8 houses (on my side) down.

It just strikes me that with 240V available the requirement
for 120V should be dwindling.

240v has been widely avaiilable here since before WW2.

My expectations are that since power use is likely to decrease, and the
power drain of household equipment of a kind is generally decreasing,
there's no push for more 220 volt usage in homes.

220 volt portable houshold appliances are rare. Just a random thought but
the advent of 90-250 volt wall warts and other stuff with similar switchmode
power supplies are opening the door to future implementation of more 220
volt house wiring.

The most recent *big* user of 240 volt power was air conditioning, but
almost all of that equipment that is going to exist has probably already
been isntalled, except of course new homes. I don't expect a lot of new
homes to be built for many years.

It really is too low for even distribution within a house.

I would say that its biggest problem is that 12 guage copper wire is getting
to be pretty expensive.

I have experienced lights dimming
significantly when appliances are turned on in many American homes.

Historical artifacts. I just rewired part of my daughter's ca. 1955 house
and all I can say is that we added a ton of new circuits and I saw many
strange things that we made go away.

Several hundred dollars worth of 12 gauge Romex and accessories were
involved. Simple things like putting the garbage disposal, microwave, and
toaster oven each on their own circuits make a big difference.