Ease of entry is crucial to well-functioning electricity markets. This paper investigates the patterns of entry in the generation segment of the electricity industry of OECD countries and seeks to provide an understanding of their key determinants. It aims to derive implications for the design of policies aimed at spurring competition under significant renewable policy objectives. The analysis focuses on investments in renewable-based electricity generation in all OECD countries over the period 1990-2007. Hypotheses drawn from the literature are tested empirically with using a panel data set based on UDI’s World Electric Power Plant Database. Findings suggest that the likelihood and the volume of entry in renewable-based power generation technologies are significantly affected by industry regulation, renewable support policies, local structural industry characteristics, such as concentration, sectoral expansion and the share of renewable-based capacity already present in the host country. Finally, micro-level factors such as the size of the (parent) firm, its experience with renewables, and whether it is a utility company, are found to significantly affect firm-level investment and entry decisions.