All conutries are faced the problems of the traditional energies are consuming, even United Nations Framwork Convention on Climate change asks the industry contries to reduce the pollution air, so it is a trend for looking for the subtitution energies. Actually, Taiwan is suitable place and the effect of green architecture to develop solar potovoltaic systems, it result in promoting the plans for Building-integrated photovoltaic systems. After the censusing, the public have lower wills to install the systems, because they needs higher prices. Although, in this research, it will point of view from the public to discuss the effect of financial payback on solar photovoltaic systems. By the analysis of simulation the single case and alternate the cases find out the trend of costs changing. Besides, the research will provide some choices of policy decition to government, and try to find out the best financial payback policy. At last, in this research it will calculate the net presnet value to compare the alternate cases which will suit for the public