Feedback is a promising strategy for energy conservation, and many energy feedback products (i.e. technologies with hardware) and platforms (i.e. technologies without hardware) have emerged on the market in recent years. Past research suggests that the effectiveness of feedback varies based on distinct characteristics, and proposes categories to better understand and distinguish between these characteristics. A review of existing categories, however, identified the following issues: (1) current structures group feedback technologies into four (or fewer) categories, making device distinction and selection onerous; (2) current categories often ignore technical and psychological distinctions of interest to researchers; and (3) none provide a systematic description of the specific characteristics that vary by category. This paper presents a classification structure of feedback technology, derived theoretically from a review of relevant literature and empirically via content analysis of 196 devices. A taxonomy structure of feedback technology was derived based on the characteristics of hardware, communications, control, display, and data collection. The resulting taxonomy included the following nine categories: (1) information platform, (2) management platform, (3) appliance monitor, (4) load monitor, (5) grid display, (6) sensor display, (7) networked sensor, (8) closed management network, and (9) open management network. These categories are mutual exclusive and exhaustive of the identified technologies collected and are based on characteristics, which are both stable and important to feedback provision. It is hoped that this feedback classification will be of use to both researchers and practitioners trying to leverage the potential of these technologies for energy conservation.