Marginal CO2 cost pass-through under imperfect competition in power markets

In line with economic theory, carbon ETS determines a rise in marginal cost equal to the carbon opportunity cost regardless of whether carbon allowances are allocated free of charge or not. This paper aims at evaluating to what extent firms in imperfectly competitive markets will pass-through into electricity prices the increase in cost. By using the load duration curve approach and the dominant firm with competitive fringe model, we show that the result is ambiguous. The increase in price can be either lower or higher than the marginal CO2 cost, depending on several structural factors: the degree of market concentration, the available capacity (whether there is excess capacity or not), the power plant mix in the market and the power demand level (peak vs. off-peak hours). The empirical analysis of the Italian context (an emblematic case of imperfectly competitive market), which can be split into four sub-markets with different structural features, provides a contribution supporting the model predictions. Market power, therefore, would determine a significant deviation from the "full pass-through" rule but we cannot know the sign of this deviation, a priori, i.e. without before taking carefully into account the structural features of the power market.