We increasingly see smart energy technology moving into peoples’ homes, designed to support householders in strategically managing different forms of energy conservation. Often, design visions for such technologies assume householders will accept smart energy systems as long as the interaction remains effortless, efficient, and convenient. Likewise, developers rely on assumptions that smart energy technologies meeting such usability goals may urge householders to become active players in a future energy market. Yet, a growing body of HCI research illustrates that actively engaging people with sustainability issues through technology requires more than merely meeting usability goals. Against this backdrop, our study investigates the design vision of a cutting-edge home energy management system created as part of an EU project and householders’ expectations of it. Our findings highlight (mis)alignments that emerged from a questionnaire study with 167 households participating in a field trial of the developed technology. We use the insights to discuss the alignment of sustainable visions, HCI, and the design of future energy systems.