Does he get into the feasibility/cost of his proposal?
I think he touches on a few concepts here and there. I'll try to skim through the final chapter again tomorrow and see if I can't find some excerpts. He does seem to focus a bit more on concepts than facts and raw data though. But I think in his defense, this book was written ten years ago and the amount of data and real world examples we can pull from today is much more vast than when the book was written.
In his argument against big power, I do distinctly remember him talking about the challenge of collecting energy from one location only to ship it over power lines to a location far away. Building the infrastructure is costly by itself and due to physics, the longer the distance you transmit electricity, the more you'll lose. So in that sense, he does talk a bit about efficiency and cost.
It's an interesting book. If you have a gap in your reading list you want to fill, you might like it.