Abstract. The aim of this paper is to provide a comparative assessment of the innovation effects of instruments which support the diffusion of renewable electricity technologies with a functions-oriented technological innovation system perspective. The paper provides a link between two major streams of the literature: the functions of innovation systems and the literature on renewable electricity support schemes. We show that, when a functional perspective is adopted, feed-in tariffs are likely to be superior to other policy instruments (quotas with tradable green certificates and tendering), although they still need to be complemented with other instruments, most importantly, direct R&D support. Furthermore, those innovation effects are affected by the specific design elements of the instruments chosen.