Positive perception of renewable energy systems, including shallow geothermal systems, is essential for a sustainable energy transition. However, it is underexplored how citizens’ feelings towards and evaluations of this technology change over time and consolidate into a stable, positive perception. In an online longitudinal experiment in Western Switzerland (Time 1: N = 823, Time 2: N = 342, Time 3: N = 221), we investigated i) how informing citizens about twenty positive or negative aspects of shallow geothermal systems change their affect towards and evaluations of the technology, ii) if such changes are stable over time, and iii) how individual differences influence these processes. Results of Time 1 (pre-information) indicate affect is positively associated with shallow geothermal systems’ evaluations. At Time 2 (post-information, three weeks later), citizens significantly updated their affect and evaluations with the information provision. The effect was double for negative over positive information, and enhanced by citizens’ biospheric values. At Time 3 (three months post-information) changes were partially retained only in the negative information condition. In informational campaigns, we thus recommend focusing on reducing the effects of negative messages while tailoring positive messages around citizens’ values, to minimize the temporal decay and maximize the positivity of geothermal systems’ image in the public's eye.