In this thesis, we are going to examine the impact of the European Union Emissions Trading Scheme (EU ETS) on wholesale electricity prices. To do so, we will look into 1. the factors that affect the EUA prices and 2. the passthrough rate of the European Union Allowance (EUA) prices to the wholesale electricity prices. This way, it will be easier to quantify the impact of the EUA prices on the electricity prices in the past but also, we will be able to make an educated prediction for the future (mainly in the medium-long term). The main problem is that the EUA prices are affected by a wide variety of factors, and due to the significance of the EUA prices to the wholesale prices, many energy market players are having trouble planning their strategies, because of the extreme fluctuations of the Wholesale electricity prices. This research will be a step toward understanding and quantifying the fluctuations of the power prices that are caused by the fluctuations in the EUA prices. We are going to examine the EU ETS history and draw some conclusions regarding the changes in its structure and its scope and the impact on the EUA prices. Moreover, we are going to use some statistical analysis to conclude the case of the post-Target model Greek Day-Ahead Market (DAM) and illustrate the bidding patterns of the Greek power producers following various factors and their marginal cost. Last, we are going to implement an OLS to the Greek DAM and provide robust evidence that the passthrough rate of the EUA price to the Greek DAM is 94% and then we will combine all of the above in an attempt to quantify the impact of the EU ETS to the wholesale electricity prices in Europe as the conclusion.