David MacKay's book is great, but it was written in 2009. Just re-reading the part about solar panels from the perspective of 2021 is quite eye-opening. He make

David MacKay's book is great, but it was written in 2009. Just re-reading the part about solar panels from the perspective of 2021 is quite eye-opening. He makes assumptions like 10% efficient panels (panels today are probably 18-22% efficient) and says that the required solar power would be "100 times all the photovoltaics in the whole world". The amount of energy he's talking about - around 1200 TWh - is now only 1.4 times all the photovoltaics in the world. In fact, last year the UK alone generated 11.77 TWh - which is about what the entire world generated in 2009 when the book was written. His book also doesn't really take into account efficiency savings. For example, his "Cars" section calculates 40kWh/day/person - or 0.8 kWh/km (1.25 km/kWh). An average electric car today might get 3 miles/kWh (4.8km/kWh) - as there's no highly inefficient internal combustion engine involved. Likewise his heating section doesn't take into account energy saving measures and it doesn't account for heating from heat pumps. It's also exceedingly unlikely that we'd use solar power in the UK to create fuels for aircraft or ships. So while David does make a good point (I think the book, overall, is excellent and I recommend it frequently), it also overstates significantly the energy required from renewables in the UK.