Assessing the impact of forward trading, retail liberalization, and white certificates on the Italian wholesale electricity prices

How do policy actions affect the dynamics of deregulated electricity prices? We investigate this issue in the context of the Italian Power Exchange (IPEX), using data on the daily average day-ahead price (PUN) between April 2004 and December 2008. Estimates of baseline time series models (SARMAX and SARMAX-EGARCH) and their forecasting performances suggest that the trend in natural gas prices, market power indicators, deterministic weekly patterns, perceived temperatures, persistence in conditional volatility, and the inverse leverage effect are essential features of the PUN dynamics. We then augment the best-performing models with dummies that account for changes in the market architecture, such as the introduction of contracts for differences (CfDs) to support renewables, trading of white certificates for energy efficiency, and the demand-side liberalization. The findings show that changes in the market architecture affected both the PUN level and its volatility. Specifically, wholesale electricity prices and volatility appear to have decreased upon the introduction of CfDs, only to be pushed upwards following the start of white certificates' trading and retail liberalization. Moreover, after controlling for reforms the inverse leverage effect vanishes, and the persistence in volatility is lower than in the baseline estimates. (C) 2011 Elsevier Ltd. All rights reserved.