Using step up / down transformers?

@sns, 
''IMO, amps should be on their own dedicated 10 gauge ac line, nothing else on that line.''

I agree 1000%. 

Let's say that a 120 volt line (load) is drawing 10 amps. Since it is a single ended design, the draw will be carried by the hot conductor. 
 By the same token, using the same example of a 10 amp draw, a 220 volt line will still draw (or I should say the load will draw) 10 amps total, BUT since it is a Balanced design, each conductor would be drawing 5 amps. The total is the same. The word efficiency, may be applied to the fact that a smaller gauge wire can then be used. 
 I have heard however that there is an increase in efficiency of electric motors because the power is coming at opposite phases (times).

@cleeds, 
Remember: Volts/amps.
Maybe this will help.

P = I x E
P = Watts, Volt-amps.
I = Current, Amps.
E = Voltage.

Will a 240V 1500 watt space heater connected to a 240V source produce more heat than a 120V 1500 watt space heater connected to a 120V source? No.....
Current, amps?
P / E = ?
1500W / 120V = 12.5 amps.
1500W / 240V = 6.25 amps.

ditusa

@cleeds,
Remember: Volts/amps.
Maybe this will help.

@ditusa you are confused. 240VAC is not more efficient than 120VAC. You apparently believe than amperage is a measure of power, which is mistaken.

Power is measured in watts. To calculate power, you multiply the amperage (which only measures the flow of current) by the voltage.

You’d probably benefit from reading a basic text in how electricity works.