I should probably back up a little. There are a couple of issues here, - generation and consumption. From my perspective, no matter how you generate it, our level of consumption is not sustainable. Solar, wind, and other renewables may be better than fossil fuels, but you can't tell me that there won't be negative environmental impacts from covering deserts in the Southwest with solar panels, transmitting half of the power to the North, - and losing 6% of that in the process.
We were able absorb the costs associated with transmission loses in the past because power generation was artificially cheap and we didn't make the generators pay for the environmental impacts. The other problem with transmitting power over long distances is that it ultimately creates more points of failure and a more fragile system.