The main point that I took away from the book is the phrase that country-scale generation using wind and solar requires country-sized installations. While it's

The main point that I took away from the book is the phrase that country-scale generation using wind and solar requires country-sized installations. While it's great that the cost of solar is falling rapidly, there's still a theoretical maximum efficiency which we can ever reach. IIRC that's around the 30% mark, and the updates in the OP suggest that for large-scale panels the efficiency has increased from around 10% to around 16%. It discusses other possible but unproven advances which might increase the efficiency more (multi-layer tech, for example). They say: "...companies are now developing multi-layer PV panels that will deliver (although timing remains uncertain) efficiencies greater than 30%". While this is clearly excellent news, it's still only a possible 3x improvement in the future which means we just need installations the size of a smaller country. Basically, it doesn't matter that the cost has dropped if we simply can't generate enough electricity that way. They discuss the possibility of generating 50% of the UK's total energy needs (not electricity needs) via solar and point out that it's not as ridiculous an idea as it was when Dr McKay wrote the book, but it's clear that we still need some fairly massive increases in technology to get there - e.g. storage, transport, routing. Perhaps they will happen quickly or perhaps they won't, it's very hard to tell at this stage. tl;dr: I'm really happy to read that solar is improving, but price alone is not the only factor. It's a big one, but it's far from the only one. Edit: also, in case it wasn't clear - I'd be ecstatic if this data were kept up to date. I was actually wondering about this just yesterday.