Germany is at risk to miss most of its self-set environmental targets for 2030. Not least, the transition to renewable energies (Energiewende) is a major challenge for politics and law. As a sub-sector, the legislator promotes the expansion of renewable energies, in particular through financial assistance for energy producers. For political and legal reasons, the volume of the funding is determinated by open competitive bidding. The detailed procedure is regulated in the Renewable Energy Act (EEG) of 2017. The tendering process serves a variety of purposes: cost efficiency, controllability of expansion, social acceptance of the transformation process and the diversity of energy producers. The following paper aims to show how the Renewable Energy Act pursues these goals and to highlight still unresolved challenges in this regard.