A photovoltaic system (PV system) is an environmental friendly power generation system. However, PV system’s installation ratio in Japan is still small. For its smooth increase, a questionnaire survey and a conjoint analysis have been done for understanding consumer’s willingness. The survey was done by mail to inhabitants in 22 prefectures considering irradiance climate categories, because there are varieties of installation ratio between prefectures. From the survey, 61% are interested in the photovoltaic systems. Major reasons were “saving utility cost”, “mitigating global warming”, and “backup for emergency”. Rest of the answers corresponding to 39% is not interested. A major reason was “expensive installation cost”. On the other hand, possible investment for the photovoltaic systems was that 5% chose 2,000,000 yen, 19 % chose 1,000,000 yen, and 35% chose 500,000 yen. 39 % chose “I do not invest”. Then, an analysis on choice probability has been done. Comparing three initial costs of PV systems with same cost pay-back time, highest choice probability was the lowest initial cost. That is, lower price of PV systems will be preferred even they are same cost pay-back time. In addition, “willingness to pay” was evaluated by the conjoint analysis. The willingness to pay for 10,000 yen utility-cost-saving was approximately 50,000 yen. This means that cost pay-back time is 5 years. Moreover, cost pay-back times of the irradiance climate categories were calculated. They were 4.6 to 5.2 years, in which no clear differences or relations with the climate categories were obtained.
