In line with empirical evidence from seminal research, we assume that emotions and social norms play a key role in consumers' decisions. To this end, we develop a socio-cognitive agent to examine the psychological and sociological factors influencing consumer decision-making. The underlying assumptions are operationalized in a decision model that integrates motivation, emotion, and normative mechanisms using a unified activation and valuation framework. A simulation of prompting other consumers to switch to green electricity via social media demonstrates how the interplay of input parameters, given by the agent's internal and external environment, memories, and personality determine the agent's decision by activating and valuating actions. Such simulations enable examining the impact of social media messages on consumer decision.