Knowing where to go: The knowledge foundation for investments in renewable energy

•We take stock of our existing knowledge foundation for decision-making regarding RE policies.•We identify major shortcomings in the currently available data on energy investments.•We emphasise shortcomings in the delineation of the sector, activities and actors.•We advocate focusing on investment data to assess future transition problems and potentials.•We provide suggestions on what micro-level data is needed for future-oriented RE policymaking.

Energy policies are increasingly focused on promoting the transition towards a more sustainable energy system. Evidence-based decision-making regarding such policies needs a solid knowledge foundation. We take stock of our existing knowledge regarding the statistics and data that form the basis for research, policy and business decision-making regarding investments in renewable energy (RE). We point to several types of problems and challenges related to achieving a statistical overview of investments in the energy sector, and argue that addressing these problems is not simply a matter of intensifying existing statistical efforts and improving precision because they are caused by fundamental difficulties. We particularly emphasize the role of investors as a linkage between public policy and firm-level activity, discussing the kind of data needed to sufficiently identify investors and their activities and fulfil their particular information needs related to investing in the RE sector. This information is important not only in research and policy contexts, but also for investment behaviour.