Bottom-up processes of policy convergence are increasingly discussed as a substitute for the absence of supranational energy policy coordination and harmonization in the EU. The overall objective of this paper is to analyse the development of government support to renewable energy R&D across EU countries over time: does the empirical evidence suggest bottom-up convergence? In order to answer this question, we first construct country-specific R&D-based knowledge stocks, and then investigate whether the developments of these stocks tend to converge or diverge across EU countries. A data set covering 12 EU Member States over the time period 1990-2012 is employed to test for the presence of conditional â-convergence using a bias-corrected dynamic panel data estimator. The empirical results are overall robust and suggest divergence in terms of public R&D-based knowledge build-up in renewable energy technology. This finding is consistent with free-riding behavior on the part of some Member States, and the presence of industrial policy motives in other States in combination with agglomeration effects in the renewable energy sector. Energy import dependence and electricity regulation are found to influence the growth of the R&D-based knowledge stock, and the deregulation of the EU electricity markets has tended to contribute to a lower speed of divergence.