Various behaviours we more or less take for granted in our everyday lives account for a steady increase in global energy use. With respect to household energy use, an increase can be observed in both amount and use of household appliances. There is evidence to suggest that household energy use is a major contributor to the greenhouse effect, and therefore households constitute an important target group when it comes to reducing energy related problems. In addition, household energy use has increased rather than decreased during the last decade. When it comes to resolving energy related problems, technological innovations (such as the development of energy-efficient appliances) are important, but behavioural changes are of equal importance. Household energy use can be divided into two broad categories. Direct energy use is related to the use of gas, electricity and fuel (e.g., heating, air conditioning, gasoline use). Indirect energy use can be described as energy use related to the production, transportation and disposal of consumer goods. To illustrate, the production of meat and vegetables requires energy, because these products need to be transported from the farm, or the greenhouse, to the supermarket. In fact, the impact of indirect energy use is rather substantial. Therefore, research on reduction of household energy consumption should focus on direct as well as indirect energy use. Many social psychological studies have investigated the effectiveness of interventions to encourage households to reduce their energy use. A commonly applied strategy is giving households information about their energy use, and/or ways to reduce it. It appears that information is definitely necessary for brining about behavioural changes, but that it works best when used in combination with other strategies, such as feedback. Providing households with feedback appears to be effective, especially when the feedback is given frequently. This way, households can see whether their efforts to reduce energy use have been worth while. A third intervention that has been investigated is goal setting, which provides households with a reference point. This intervention also proved to be most effective in combination with other interventions. Environmentally significant behaviour, such as energy use, can be characterised as a social dilemma, because of the conflict between individual and collective interests. Individual advantages of energy use are often immediately visible (e.g., comfort), whereas the consequences for the collective (e.g., emission of greenhouse gases) are only visible in the long run. Moreover, outcomes of individual behaviour depend to a large extent on what other people will do (interdependency). The following variables were included in the study, for they may influence behaviour in a social dilemma: collective interests (e.g., problem awareness), individual interests (e.g., attitude towards energy conservation), social norms/trust in others’ contribution to the problem (what do other people do when it comes to conserving energy), and self-efficacy (perceived possibilities to reduce own energy use). The present study has a multidisciplinary focus: the research team consists of psychologists, environmental scientists and computer engineers. In this applied social psychological study, households were encouraged to reduce their energy use by at least 5% by means of giving tailored (viz., highly personalised) information through the Internet. Against the background of a social-dilemma model, a combination of strategies for behavioural change (viz., tailored information, goal setting and feedback) was tested in a quasi-experimental design. Half of the participants only received feedback about their own energy savings (individual feedback), the other half also received feedback about how the participants as a group were performing (comparative feedback). A control group did not receive any information, goal setting or feedback. In addition, it was investigated which psychological factors underlie household energy use and energy savings. Results indicate that households who received tailored information and feedback saved more energy than the control group did. Furthermore, results suggest that especially informing people of relevant energy saving options caused this effect. More detailed results will be presented at the conference.