Enabling an integration of large amounts of variable renewable energy (VRE) into an energy system is an important contribution to reduce part of its associated carbon dioxide emissions. A resulting challenge from integrating VRE is an increase in mismatch between supply and demand which could be reduced by increasing demand side flexibility in the residential sector by shifting energy using behavior. This thesis offers a theoretical and empirical analysis of energy using flexibility based on behavior analysis principles to relate what it can mean to account for a human dimension in an electrical energy system. To characterize degrees of freedom in allocating behavior and options for flexibility of energy using behavior, variability of behavioral patterns in terms of homogeneity between individuals is analyzed. Notably, even in times for which one could principally expect more variability between behavioral patterns such as in the afternoon and evening, one finds that behavioral activities are pre-structured, clearly limiting the possibilities for shifting energy using behavior. The behavior analytical perspective highlights the importance of addressing context structure and associated behavioral effort for shifting behavior, when addressing the challenge of mitigating the mismatch problem for a more sustainable energy system.