Our Goal: To develop a multimodular intervention aiming to improve competence, motivation, and supervisor support of heating technicians to promote more energy-efficient heating system adjustments and thus reduce the energy demand of energy-intensive buildings. The Intervention: Heating professionals were provided with a check-list in the boiler rooms to structure their work tasks, allow individual goal setting, and – depending on the experimental condition – get feedback from their responsible supervisors. The Results: We predicted reduced actual energy consumption in the buildings where responsible heating technicians were assigned to one of the experimental conditions compared to controls. We did not find this consistently across experimental conditions. Lesson Learned: Implementing behavioral interventions to increase energy efficiency of professionals should encompass various levels, including interventions at the level of the supervisor – which seems to be the most promising approach to foster behavior change in the given context.