The scalability of deep-tech startups in the renewable energy sector depends not only on firms' technological capabilities but also on the interaction among economic conditions, financing, market structure, technology, supply chains, human capital, and the policy environment. This study aims to explore the contextual dimensions underlying the formation of a policy window for scaling deep-tech startups in Iran's renewable energy sector. The study is theoretically grounded in Kingdon's Multiple Streams Framework and adopts a qualitative research design using Braun and Clarke's thematic analysis. Data were collected through 23 semi-structured interviews with experts in energy, policymaking, innovation, and entrepreneurship. Thematic analysis resulted in seven major themes and 22 subthemes. The findings indicate that the economic environment, financing, market, technology, supply chains, human capital, and policymaking constitute the major dimensions shaping the formation and exploitation of the scalability opportunity window. Within the Multiple Streams Framework, the intensification of the national energy imbalance represents the problem stream, the emergence of domestic technological capabilities represents the solution stream, and growing policy and industrial attention to energy diversification constitutes the political stream. The MICMAC analysis further revealed that economic instability, policy instability, and institutional and regulatory barriers function as major driving factors, while financing, technology access, commercialization, and market acceptance occupy linkage positions. Factors related to market opportunities, technological benefits, supply chains, and human capital are predominantly positioned as dependent variables. These findings suggest that exploiting the emerging policy window requires a shift from fragmented support measures toward coordinated governance, regulatory stability, tariff reform, long-term financing mechanisms, stronger industry–innovation linkages, and reduced policy uncertainty.