<p>Clean energy adoption is crucial in combating climate change and crowdfunding, when aligned with investor preferences, can play a pivotal role in accelerating the clean energy transition. However, little is known about what drives crowdfunding investment decisions. This study employs a Fuzzy-set Qualitative Comparative Analysis (fsQCA) to examine 88 solar energy projects in Spain and Italy, identifying the key factors that influence investor behavior in clean energy crowdfunding. We analyzed six causal conditions: maturity period, risk, minimum and maximum investment amounts, CO₂ emissions savings, and offered yields. The analysis revealed that no single condition is necessary for investment success, but several configurations are sufficient to explain high or low investment motivation. Specifically, short maturity periods and low-risk levels consistently appeared in successful funding configurations. Profitability and environmental impact (CO₂ savings) played supportive, though not standalone, roles in attracting investment. Results suggest that investors in clean energy crowdfunding are generally risk-averse and prefer short-term returns, even when environmental benefits are substantial. Projects with high CO₂ savings can attract funds when paired with high yields and manageable risk. Conversely, high-risk or long-term projects tend to underperform, even when paired with high potential returns or environmental benefits. Hence, policymakers and crowdfunding platform designers should prioritize low-risk, short-term projects, establish accessible investment thresholds, and enhance transparency in environmental impact reporting.</p>