[Arct1k]

Ohms law covers this...

Power = current X current x resistance

Power = current X voltage

So for constant a power output ( amps x volts) the loss is the square of the current. Hence to raise the power by a factor of 2 - raising the voltage by a factor of 2 keeps the loss constant - raising the raising current by a factor of 2 to achieve the same result raises the losses by a factor of 4 - i.e 4 times as much heat!

This is why power lines are at 100,000 volts....