From what I understand even at 100 miles the loss of energy is about 5 percent. You may need to build more transmission lines at some point - but I would still wager there is no way that it is energy efficient to build a frame upwards + have people get on special tools to maintain things 10 feet above the ground.

In places like Colorado there is very cheap land that is not very good for farming about an hour away from Denver and it certainly seems like it would be cost + energy efficient to build out there instead of up.

I'm not arguing for a giant solar array in the Sahara, just using marginal farmland that surrounds many cities to put solar panels instead of scattered about on roofs in the city. And with most solar installations it just dumps electricity back into the grid so I'd think losses would be similar.