Networks of low-cost sensors make it possible to track human behavior wherever we are and whatever we do. While behavior change programs in the past were often designed in an paternalistic spirit of “educating the masses”, technology-based behavioral interventions can tap into different mechanisms and be tailored to the specific context and needs of the individual. An increasing number of studies in the health and energy sector already show that technology-based behavioral interventions can cost-effectively induce behavior change on a large scale. In a prior field study, we have shown that feedback on the resource consumption of a specific activity (showering) induced a 22% conservation effect on the target activity. In a follow-up field study with 720 Swiss households, we now investigate why this technology-enabled approach is so powerful: is the large conservation impact due to a) attention drawn to the energy-intensity of the behavior, b) the correction of misconceptions about one’s environmental impact, c) behavioral control (the assessment of one’s performance against reference points) or d) explicit performance appraisal?