Readers revisiting David MacKay's 2008 book Sustainable Energy Without the Hot Air praise its quantitative approach but criticize its primary energy fallacy of directly comparing chemical and electrical energy without accounting for efficiency differences. Discussants also note that the text's renewable energy forecasts are outdated due to massive technological advancements and price drops in solar and wind over the past decade. Nevertheless, defenders maintain that the core message remains relevant, highlighting that while renewable electricity is rapidly expanding, fully decarbonizing total global energy consumption still requires significant progress in storage and electrification.