The comparison of solar energy technologies with conventional technologies involves more than just comparing the costs of supplying energy and provding capacity. Solar technologies supply energy in a sustainable manner while having minimal effects on the environment. When choosing between solar energy technologies and conventional technologies, first cost is a important factor. The environmental and other social benifits of using solar energy technologies contrasts sharply with the environmental degradation and social costs resulting from the use of conventional technologies. These hidden costs, sometimes called "social cost", are not included in conventional economics. This paper is emphasized that the consideration of social costs effects comparisons between renewable and conventional energy technologies is of importance.