On the Efficiency of the EPEX Day-Ahead Spot Market

In this paper we investigate the efficiency of the day-ahead market for electricity at the EPEX, the largest central European market for electricity. To analyze whether generating companies use their market power to influence prices, we used a conjectural variations approach for the years 2007-2010 on a yearly basis as well as a direct approach for estimating marginal costs for the year 2010. The results of both approaches show no indication for systematic abuse of market power by the suppliers of electricity on the EPEX day-ahead spot market for the analyzed period of time. Conducting the same analysis for high load hours, which are generally considered to be the most prone to market manipulation, yielded similar results suggesting that the results are robust. For our analysis, we considered hourly price and demand data and consequently obtained a high level of statistical significance in our models.