Eco-visualizations (EVs) are any kind of interactive device targeted at revealing energy use in order to promote sustainable behaviours or foster positive attitudes towards sustainable practices. There are some interesting, informative, highly creative, and delightful EVs now available. This paper provides a critical survey of several noteworthy EVs and classifies them in terms of scale and contexts of use. The paper attempts to provide a foundation for practitioners to design new EVs in more varied scales and contexts and for researchers to continue to refine understandings of how effective EVs can be and how EVs can be made to be more effective. The paper describes (i) feedback types and use-contexts for classifying EVs and (ii) strategies for designing effective EVs.