For very long distance power transmission, losses primarily depend on voltage and AC>DC>AC conversion efficiency which have both been increasing. China just completed a 3,300 km (2,100 mi) 1,100 kV line capable of sending 12 GW at the cost of 5.9 Billion dollars.
Over 1500km you can keep losses under 10%, but building infrastructure isn’t free. East to West links tend to work better because you can time shift demand and thus build fewer power plants.
Over 1500km you can keep losses under 10%, but building infrastructure isn’t free. East to West links tend to work better because you can time shift demand and thus build fewer power plants.