In the pursuit of sustainability there is much talk about the need to increase energy efficiency but much less discussion about what this actually means. When economists and engineers talk about efficiency they are rarely talking about the same thing, with economists typically focusing on money and engineers more often focusing on electrons. For example, economists believe it is efficient to leave the lights on all night if the person paying the bill dislikes turning them on an off more than they dislike paying their electricity bill. In this talk, Richard will discuss the implications for those interested in the pursuit of sustainability of relying on the economists or engineers definition of efficiency before declaring who is right and who is wrong.
