Arguably, a great number of environmentally relevant behaviors take place within the family home. One interesting feature of household environmental behavior is that strong normative control can be executed by household members simply because they are in the position to actually observe the behavior of the other group members on a permanent basis. A second feature is that household members will, more often than not, consider themselves to belong to the family, which may have substantial influence on the perception of their social identity. We reasoned that these family dynamics might exert their influence through personal and social norms regarding the performance of environmentally relevant household behaviors. We hypothesized that personal norms and social norms will congrue in predicting behavior when social identity is high, and will contribute independently when social identity is low. We investigated whether the joint contribution of personal norms and group norms to explain the proenvironmental achievements of the group, i.e., the family, was moderated by social identity regarding two behaviors for which varying degrees of group interdependence exist in realising optimal environmental performance. Proenvironmental acts within the household clearly differ in the extent to which members of a group depend upon each other in obtaining the desired result. For some behaviors the action of one group member is sufficient to obtain the desired result for the whole group, for other behaviors each group member can contribute independent of others. Two questionnaire studies were performed to explore the merits of this conceptual framework on behaviors with different levels of group dependence. In the first study (N=190) the focal behaviors were closing the curtains in the living room (low group dependence), and the time group members spend showering (high group dependence). In the second study (N=163) the focal behaviors were lowering the thermostat of the central heating well before going to bed (low group dependence), and switching off lights in rooms that were not used (high group dependence).