In this article, we give insights into the development of an ‘interface of energy’, which is developed as part of the energy turnaround project ‘enera’. This interface shall allow communication between the human and the future energy network which will be dominated by renewable energy sources and on-site power generation. We show how we applied Human-Centered Design methods to address the challenge of designing a user interface for an infrastructure that is still in development. Further, we show how this approach was successfully combined with public relations, such as feedback sessions on prototypes as part of an open Barcamp. We give insights into interviews, profiles, personas, public operations, user needs, prototyping and testing. As a special feature we conducted prototyping and prototype testing workshops in a residential house within the project region. These turned out to be very successful for many reasons, e. g., in that the natural environment served as a creative stimulator. Besides, the workshops had a lasting effect on the participants, who were members of the project as well as volunteers living in the project region.