Green building is a sustainable ecological building, and the application of renewable energy to green buildings can protect the ecological environment and reduce energy consumption to a certain extent, so this paper makes an in-depth analysis of the impact of renewable energy application on the cost of green building projects. Firstly, the grey correlation analysis was used to analyze the characteristic indicators of renewable energy applied to the cost of green building projects, and the estimation index system of green building projects was constructed. Then, the improved genetic algorithm was used to construct the explanatory variables and control variables of green building project cost control, the variation factors of green building project cost control were analyzed through principal component analysis, and the elastic modulus and regression discriminant method were combined to complete the impact analysis of renewable energy application to green building project cost. The simulation results show that the algorithm can effectively reduce the economic cost of green buildings, ensure the quality of buildings, and protect the natural ecological environment.