One aspect of the energy debate that has received little attention is behaviour. We argue that the starting point for any approach to energy system development must be efficiency of both demand and supply sides. In general, the efficiency of the supply side is driven by technological developments in response to policy changes or new developments such as biofuels. Technology and new developments also influence the demand side. But lifestyles, how we view and use energy services, is an increasingly important factor implying a significant role for social learning.