The way users interact with systems requiring energy largely conditions their global environmental impact. Informing of the environmental consequences of usage of products/systems can generate increased awareness of its connection to environmental impacts, encouraging a change in user behaviour and resulting in products' global environmental impact. Various levels of product modification have been proposed, from simple information, through behaviour steering and persuasive technology. We focus on eco-feedback and distinguish three different modalities: neutral, positive and negative. Based on the conclusions of an experiment observing the consumption of paper towels, this article demonstrates: (1) An individual's general level of information about the environment has an influence on the effectiveness of the eco-feedback modality. (2) The effectiveness of a modality of eco-feedback diminishes over time. The potential of iterative user feedback combined with intelligent sensor embedded systems led to our defining the Green Use Learning Cycle as an innovative concept for eco-design. It underlines that products should be designed so that they can give feedback to users about the environmental performances of their usage (user adapts to product), and can analyse the dominant parameters of usage to be configured automatically to the environmental optimum throughout the life cycle (product adapts to user).