Decision science literature argues that conventional opinion surveys are limited for making strategic decisions because the elicited opinions may be distorted by misconceptions and awareness gaps that prevail in the public. Such distortions are in particular expected for new technologies, such as Enhanced Geothermal Systems (EGS). We created an informed citizen panel (N=46) for understanding the preferred Swiss electricity mix in 2035, given the information about environmental, health, economic and accident impacts of various electricity generation technologies. We used technology factsheets, an interactive web-tool Riskmeter, and group discussions for informing the participating citizens. We then measured the evolution of the panel's knowledge and preferences from initial (uninformed) to informed and longer-term views four weeks after. For EGS, we found that the participants were in particular sensitive to new information as they did not yet have stable opinions formed and, in fact, with more information the opinions worsened. Induced seismicity risk was one of the elements that was used by our participants in their opinion formation, but also land use, climate, and electricity supply reliability impacts as well as the overall comparison with other technologies. We also found structurally different pattern in the evolution of opinion for EGS and other renewable electricity generation alternatives. We thus conclude with implications of these findings for understanding the public preferences for EGS and for communicating about it