The efficacy of digital solutions to increase energy efficiency, including technical optimisations and behavioural influence, has long been a subject of debate within sustainable HCI (SHCI). While the viewpoints of policymakers and academics are frequently published (and often contradictory), less is known about the views of those on the ground. In this paper we ask: What are energy professionals’ views of digital energy-saving interventions and their users? What are the challenges they face implementing these interventions? Based on a university campus case study with twelve semi-structured interviews and a focus group with energy and facilities’ professionals, we illustrate how they strongly advocate digital efficiency as a pathway to sustainability; yet, this optimism is in apparent tension with key barriers they identify to realising ‘their seamless visions’, particularly the complexities of the human behaviour they are seeking to optimise. These findings underscore the seductiveness of techno-optimism and the need for more systemic change.