Question

Why is it more economical to transmit electrical energy at high voltage and low current?

Answer 1

It is economical to transmit electrical energy at high voltage and low current rather than low voltage and high current for various reasons.
Power is given as VI.
So for same power, the value of current will be less at high voltage. With less current, there will be reduced transmission losses which is given by I²R
If less current is in the wire then the size of conductor required will also be less. When the size of conductor is less, then less weight poles can be used which will further save money.