The active participation of citizens is essential for the green transformation. Energy portals are playing an increasingly important role in actively engaging consumers in future energy services. This paper presents the development process of an energy portal as an innovative service for utility customers. The portal was enriched with energy community features and integrated ambient feedback. The results provide insights from a seven-month field study in which 234 Slovenian households tested and evaluated the portal. The objectives of the study were to (1) analyze the consumer onboarding process, (2) evaluate consumers’ interaction with the portal over time, (3) examine the impact of communication outside the portal on activity in the portal, and (4) evaluate the portal by the consumers. The data show that consumers are willing to try new services: with a median response time of 9 days, 86% of the invited consumers registered on the portal and 95% visited the portal within 5 minutes of registration. The survey showed that the consumers are overall satisfied with the portal (rating 3.97/5). The experience and insights gained during the study and the iterative UI design process serve as a foundation for future demand reduction and energy community services.