ISBN 978-0-9544529-3-3 (paperback). “Sustainable Energy – without the hot air” by David JC Mackay is available for free download from www.withouthotair.com. Published by UIT Cambridge Ltd in 2009. This is a review of the free download. The author is a Professor in the Department of Physics at Cambridge University so he should really know his stuff…. But, he wears shorts, rides a bike and his PhD was in Neural Systems. His research is into machine learning, information theory and communication systems whilst he has been teaching the public about energy systems only since 2005. This might make some a little doubtful about the quality of this work. MacKay bills the book as a neutral and scientific look at the debate. He relishes the lack of science in the discussion and feels the need to redress the balance. This looks like a labour of love, obviously a hobby and side-line but the amount of research in the book suggests he is well read on the subject despite his apparent lack of background in the field. Well, physics is physics. The books is very thorough although it has some major shortcomings – all of which he freely admits to. Primarily he doesn’t compare like-with-like. He totals up total energy requirements and resources without properly comparing transport fuels with transport fuels. However this doesn’t overly distract from the BIG picture he paints. He even divides the book up into sections for those who believe in Climate Change and sections for those who do not. Either way his conclusion is the same: we need to decarbonise the UK (and global) economy. Economics and finance are not fully discussed and he doesn’t properly analyse the opportunity cost of one course of action versus the other. We also don’t often get a “value for money” type analysis as to how far a dollar of taxpayer’s money would go to eliminate carbon given the different choices. The data we have suggests that Nuclear power is terrible value for money but Mackay still shortlists it without this type of input. Even with these problems there are few quibbles about the conclusions, even if they are sometimes uncomfortable. The anti-transitioners and flat-earthers will, no doubt, draw a crumb of comfort here if they cherry-pick the data. Expect this book to be quoted by BOTH sides of the argument. This is not easy reading but it certainly cuts the crap. Transitioning to a sustainable energy system will not be easy. It will cost a lot of money and we will have to cut back on our profligate use of energy across the food and transport sectors. Everything is about to change and it may not be the ecotopia that the greens imagine. It may well be that the medicine contains some bitterness and a lot of compromises. However, doing nothing is clearly not an option. Recommended.