Explanations of Energy Efficiency
Transmission lines have a built-in loss for the purpose of reducing the number of lines.
When electrons flow through metal, there is resistance which creates heat as lost energy. The smaller the wires, the more the resistance. Large wires have less resistance and less energy loss. But large wires are more expensive and take up more space.
There is so much resistance and energy loss per foot. Two feet loses twice as much energy as one foot. So long lines lose more energy than short lines.
With overhead wires in transmission lines, the strength to weight ratio for the metal is important. This means there is an optimum size for the wires based upon the strength of the metal and how close together the towers are. If more energy must flow, additional lines have to be constructed, because the wire size cannot be changed from optimum.
Therefore, if the built-in loss for long transmission lines is reduced from 50% to 25%, and for short lines, from 20% to 10%, the number of transmission lines would have to be doubled. Doubling the lines would be very expense and damaging to the environment.
If less energy is put through a line, there will be less loss. It's like a drop cord in a house. A lot of current will cause it to heat up. Less current through the same wire will lose less energy. Therefore, the operators can send less energy through a line, if they want less loss. But long lines are more expensive than the source of the electricity. So demanding lines are loaded down, which usually means operators will send through enough energy to result in 50% loss for long lines.