After installing a photovoltaic (PV) system in a house or a school. it is said that people seem to increase behavior that shows concern for the environment such as saving electricity. Do characteristics of PV systems have any influence on the change in people's behavior? This study attempts to discover why peoples behavior toward energy and the environment change after installing a PV system. Based on questionnaire surveys, this paper describes the results of statistical analysis concerning the changes in households that installed PV systems. The results show that in households where the family members are highly aware of their PV systems they tend to increase environmental behavior after installing the PV system. It is also found that an increase in communication about environmental behavior in a family tends to go hand-in-hand with the increase in environmental behavior. The findings suggest that the installation of residential PV systems affect people's concern and norms related to energy and the environment, and consequently influences people's behavior. (C) 2009 Elsevier Ltd. All rights reserved.