Adolescents are an important population to target with energy-saving\ninterventions: Not only are adolescents high consumers of energy, but\nthey are also the adult consumers of the future. In the present study,\nan online energy-saving intervention was developed based on\nimplementation intentions, a widely used psychological behavior change\ntechnique. A total of 180 adolescents, aged 13 to 15 years, were\nrecruited using purposeful sampling and were allocated to either the\nintervention or control condition. A significant increase in\nadolescent's self-reported energy-saving behavior was found among\nadolescents who had received the intervention, which was sustained at\nthe 6-week follow-up. However, some adolescents were more affected by\nthe intervention than others; adolescents who already actively engaged\nin energy saving (as identified by their readiness to change prior to\nthe intervention) reported a significant increase in energy-saving\nbehaviors as a consequence of participation in the intervention, whereas\nthose who were not already saving energy did not.