Energy efficiency is one of the main challenge of the next decades. It is generally accepted that energy consumption is determined by technology improvements, market prices, but also the lifestyles of consumers. The main objective of this project is the conceptualisation of energy models integrating variables like "behaviour and use" and "lifestyles" assuming that behavioural factors have a big impact on energy demand in residential and transport sectors. Conceptualisation of lifestyles are thought to have an added benefit for the set-up of future energy demand models.