This study examines the financial and policy conditions required to scale institutional investment in the renewable energy infrastructure of the United States. It analyzes how market instruments and demand-side policies interact to address persistent barriers that limit capital mobilization, including regulatory uncertainty, liquidity constraints, and misaligned risk–return expectations. The findings show that instruments such as green bonds, infrastructure funds, yields, and public–private partnerships improve project bankability by distributing risk, enhancing liquidity, and aligning cash-flow characteristics with long-term investor mandates. The evidence indicates that coordinated implementation of these mechanisms produces more durable investment outcomes than isolated interventions, lowering capital costs and improving investment certainty. The research highlights that expanding institutional participation in renewable infrastructure requires integrated financial structures and stable policy frameworks capable of supporting long-duration capital flows and accelerating progress toward national decarbonization goals.