Electricity generation has external costs that are mainly imposed on people who have no role in electricity generation. External or external costs are formed when the economic activities of one or more groups negatively affect another group or groups. For instance, construction and operation of thermal power plants emit carbon dioxide, sulfur oxides, and nitrogen, which can negatively affect buildings and human health. To determine the external costs of a unit, it is necessary to estimate the emission effects on the environment. In this study, the estimation of social costs of SO2, NOX, and CO2 emissions from fission and nuclear fusion power plants has been done for the first time by modifying the existing and related global coefficients. The scenarios used in the study include carbon trade scenarios and statistical indicators of life. First, a study was conducted on seven technologies in Iran, and then the results were compared to the entire world energy production industry. The final results show that the fusion and fission technologies performed well in a comparative cost analysis (161 and 127$/MWh, respectively). Also, cost analysis shows that the fusion power has the least health care costs (7$/MWh), which can be interpreted that fusion power is greener than the other powers, and after that comes fission with 24$/MWh.