Climate warming and environmental degradation increasingly threaten human survival and sustainable development. Renewable energy corporations, as the main source of clean energy, play a key role in this process of carbon neutrality. However, due to the large investment scale, strong irreversibility and high technical requirements of renewable energy projects, corporations face high business risks, which in turn have a significant impact on their investment decisions. This study measured investment efficiency indicators such as return on capital (ROC) and return on investment (ROI) and explored how business risk can moderate the investment return performance of corporations by influencing their choice of investment opportunities and resource allocation. This study used 233 renewable energy corporations in China from 2009 to 2023 and used the structural equation model (SEM) to empirically analyze the dual impact of business risk on the investment scale and investment efficiency of renewable energy corporations. The results of the study reveal that business risk significantly reduced investment scale in non-state-owned corporations whereas business risk has positive relationship with investment efficiency, particularly in state-owned corporations. Government subsidies have negative impact of business risk on investment scale and moderately significant impact on investment efficiency. There is a significant difference between state-owned and non-state-owned corporations in their response to business risks, the state-owned entities demonstrating stronger resilience in maintaining investment scale and achieving efficiency improvements under risk conditions. The findings suggest that while business risks constrain investment scale, they paradoxically enhance investment efficiency by promoting more selective and strategic investment decisions, while government subsidies play a crucial role. This study provides empirical evidence for the government to formulate more targeted support policies to for promoting the green development of China's renewable energy industry and achieving carbon neutrality goals for sustainable development.