In my current house I have done 240V/50A wiring,
240V/50A Sub Panel,
lots of 240V/30A outlets.? None of which I would advise the usual
amateur to do.? :-)
This is wise, but 240v is quite nice for computer equipment. I had an
electrician run a 240v 30a (10g wire) circuit out to my work shed, where
a subpanel is installed with 120v 15a and 240v 15a circuits for the
equipment.
240 just allows you to get twice the power to the device using the same
size wire (14g for 15a for example). But modern switching computer
supplies are more efficient at 240v than 120v so you waste less power.
120 is good for like light bulbs and stuff. Drawing over say 10a
continuous at 120 will pretty much burn up sockets and such in short order.