We examine the impact of regulation and policies on green patent generation and evolution of renewable energy technologies in the OECD countries. Public and private investment, investment in education, research and development, and environmental regulation are considered. There is considerable variation in innovation systems and investments in renewable energy, and in outcomes. We assess the impact of environmental stringency and environmental taxes and regulations on renewable energy patents. The considerable heterogeneity requires emphasis on country effects and a separation of general from specific green innovation outcomes. We account for country-specific innovation factors. A balanced panel of 27 OECD countries is examined between 1990 and 2018. A renewable patent model is estimated by different panel data models and estimation methods. We find considerable sensitivity to model assumptions and inference techniques. The study is suggestive, however, of some renewable energy approaches for achievement of OECD environmental goals.