Recently, interests in renewable energy have gradually increased. Of various renewable energy, Photovoltaic system has the properties affected by weather. This paper discusses the economic evaluation based on insolation data analysis. Real insolation data were obtained by radiation measurement device installed in projected photovoltaic system site during 20 months. Obtained real insolation data were standardized using clear day analysis. Standardized data are greater than obtained real insolation data and were used as parameters of RETScreen for the economic evaluation. In results, capacity(30[kW]) of soon cheon is shown the most B/C(1.20). Applied methods have effectively done to develop photovoltaic system.