Rethinking Notions of Energy Efficiency in a Global Context

Energy efficiency is, in principle, a simple idea: an output of human value, for example, vehicle-km traveled, divided by the needed input energy. Efficiency improvements are regarded as an important means of mitigating not only climate change, but also other environmental problems. Despite the vast number of articles published on energy efficiency, a few people question whether it is a useful or accurate measure in its present form; nearly all papers are either engineering studies, or address barriers to efficiency improvements. This review addresses this issue via a critical review of the literature, including not only papers on energy efficiency, but those on adjacent areas of research that can help broaden the scope, both geographically and conceptually. These shortcomings are illustrated in case studies of buildings/cities and road passenger transport. The main findings of this review are that (1) energy efficiency inevitably has an ethical dimension, as well as a technical one, in that feedbacks are more widespread than they have generally considered to be, and (2) that conventional efficiency measures omit important energy input items, particularly those concerned with the mining the materials needed for renewable energy plants. The key conclusions are that present efficiency measures are not adequate, and future research is needed to overcome these shortcomings.