Domestic energy consumption is continuing to increase and the need to decrease consumption is growing more evident. In this research, two studies were conducted to further the understanding of domestic energy behaviour and increase the knowledge of how energy conservation can be supported. The first study was carried out as an interview study to explore both factors that influence people’s energy behaviour and strategies people currently have adopted for reducing consumption. The second study was a field trial that assessed the extent to which an energy feedback system could support households in reducing their consumption.The findings show that many different factors, i.e., factors related to the person, the activity, and the society, influence people’s domestic energy behaviour as well as their engagement in reducing their energy consumption. As these factors collectively set the preconditions for people’s energy behaviour, it is vital to take into account the interconnection of the different factors when aiming to support energy conservation. For systems and products to be successful in supporting energy conservation, they need to match the preconditions in a way that enables people to reduce consumption while still satisfying their everyday needs and goals. As this research have indicated, energy feedback systems can support motivated people who have the ability and possibility to reduce consumption, but will be a less successful support system for people whose consumption is governed by preconditions that they cannot, or will not, change. A holistic understanding of people’s preconditions and their energy related activities is thus required in order to develop successful products, services, and systems that enable, facilitate, or encourage more people to reduce their domestic energy consumption