This thesis investigates the interplay between Power Purchase Agreements (PPAs) and wholesale spot electricity markets in the European Union (EU) using the Greek electricity market as a case study. PPAs have been an important tool in the financing of renewable power projects because they offer  producers and purchasers long-term price certainty. Meanwhile, wholesale electricity markets, operating on the basis of marginal pricing and real-time price signals, are important for both the allocation of resources and the integration of the market. The study examines how these two mechanisms interact, reinforce, or possibly clash, especially in light of the EU’s decarbonization strategy and recent regulatory innovations associated with the Green Deal and Repower EU. The research approach is mixed (legal and economic) in nature to assess the EU-wide regulatory framework and its national introduction in Greece. The Greek market is selected as a case study because of the recent electricity liberalization process, the high penetration of renewable energy sources, and its strategic role on a regional level. Results demonstrate that the successful integration of PPAs into wholesale markets can be facilitated by regulatory changes, risk-sharing mechanisms, and alignment of market rules. Finally, the thesis offers policy advice to strengthen the security of investments, the liquidity of the markets, and the long-term prospects for a decarbonized European electricity market.