As the opening chapter of this book sets out, the multi-dimensional and multi-temporal nature of energy security and the risks and threats to it, stand in the way of any simple assumptions about how to improve British energy security. The role that demand can play in improving energy security is also complex and there is currently a lack of clarity within policy discussions, with terms such as energy efficiency, demand reduction and energy conservation used interchangeably, and rarely applied with rigour. It is also apparent that the current British emphasis is on security of supply, and that demand side debates are generally characterised in terms of carbon, and therefore as if they have little to do with security. We argue that the role of demand should be central to analysis, modelling and policy to meet the goals of creating a secure, affordable and low carbon energy system.