This paper considers the debate in the UK and the USA on some economists' claims that improving energy efficiency will lead to a greater energy consumption (than would have otherwise occurred), a concept termed the Khazzoom-Brookes postulate. It analyses the criticisms of this claim and of the responses, particularly of the concept of [`]dematerialization'. The paper attempts to tackle the paucity of empirical evidence in the UK by looking at long-term trends in efficiency and use with respect to UK public lighting. Finally, it focuses on the views of two economists, namely Len Brookes and William Rees, who both accept the postulate but have differing views and policies on measures to reduce carbon emissions from fossil fuels. Brookes believes in free-market solutions, whereas Rees puts forward a vision of a sustainable future based on ecological tax-reform and reafforestation.