In this article we report about our efforts to employ detailed physical simulation models (so called digital twins) and advanced optimization algorithms to identify optimal investment decisions into renewable energy systems to reduce energy costs and carbon emissions. From our own experience and discussions with several energy consultants, we learned that even when presented with very good investment options, decision makers are very often hesitant to act quickly. In this work we argue that to tackle this problem, the psychological aspects of the optimization and decision making process need to be addressed explicitly. We review some of the main insights from psychology of decision making and propose trust as the key factor with transparency and explainability as the main necessary contributors for building trust.