In this paper we argue that energy conservation is largely a group phenomenon requiring group interventions to achieve change. Persuasive technology can help to provide these interventions. The present study explores the influence of group feedback and individual comparative feedback on energy consumption using an experimental simulation paradigm. To account for cultural differences in group orientation and the power of group feedback, two studies were conducted, one in the Netherlands and one in Japan, in which groups of participants received feedback on everyday tasks. As expected, Dutch participants saved more energy when individual comparison feedback was present, but not the Japanese participants. In contrast, as expected, group feedback caused Japanese participants to save more energy. Providing solely group feedback did not promote energy saving in the Netherlands. Group feedback made the Dutch save more energy only in combination with individual comparison feedback. These results suggest that persuasive technology can employ the power of feedback as a group intervention, but that relevant cultural orientations are crucial.