The authors performed the questionnaire survey based on the conjoint analysis in order to clarify the monetary value of the environmental performance of the detached house. The cost, locational condition, household goods and environmental performance are considered as the attributes, which affect the utility of detached house. The environmental performance is represented by the amount of the energy consumption cuts by the usage of the solar collector or the photovoltaic system. From these investigations, the monetary value of the reduction of the energy consumption based on the MWTP is higher than the market price of the both solar collector and the photovoltaic system. In addition, the MWTP of the all attributes of the house depends on the economic situation of the respondents. This tendency is most remarkable in the MWTP of the environmental performance.
