>The efficiency of high voltage AC power lines is limited by capacitive coupling to ground. As often in engineering, the sweet spot is where multiple factors h

>The efficiency of high voltage AC power lines is limited by capacitive coupling to ground. As often in engineering, the sweet spot is where multiple factors have ~equal contributions, so even a 50% win in one of the factors can't give you that much benefit. For high voltage AC power lines it's Ohmic losses, corona discharge losses, and inductive losses.