To support planning of effective and efficient energy technology development, research on methods based on energy systems analysis and cost-effectiveness analysis is conducted especially focusing on photovoltaics (PV). Based on the cost-effectiveness analysis of PV R&D and subsidization, subsidy to PV capital cost is appropriately planned because subsidization is done when cost-efficiency of PV R&D is decreased well as shown in Figure. On the other hand, by using energy system model of Japan, buy-back subsidy to photovoltaics, which makes target for PV capacity attainable by achieving goal of PV system sales price, is analyzed and the results show that it becomes unnecessary if PV can be attained 170 JPY/w by 2030.