The impact of intermittently renewable energy on Italian wholesale electricity prices: Additional benefits or additional costs?

• We use a hybrid analysis based on a combined approach (both simulation and ex-post empirical analyses).
• There is a critical threshold of RES penetration within which prices may increase.
• Price increases are more likely with PV rather than with wind power.
• Either the simulation models or the full empirical analyses may be misleading.
• Caution is necessary when using the results of these analyses for policy decisions.

Most studies of the literature find that the development of renewable energy sources determines a decrease in the wholesale prices. Some authors use this finding to state that the current subsidies for renewable technologies cannot be considered as excessive. By carrying out a hybrid analysis (both simulation and ex-post empirical analyses) of the case of photovoltaic energy in Italy, this article demonstrates that this result cannot be generalised. Under market power, an increase in PV production can provide benefits in terms of a wholesale price decrease only beyond a specific threshold and especially if combined with other effects. Otherwise, it is likely that PV development could imply an increase in prices. Therefore, on the one hand, caution is necessary when using the estimated change in wholesale prices to evaluate the net cost for consumers of the supporting policies for renewables: either the simulation-based models or the full empirical analyses may be misleading. On the other hand, if "decarbonisation" is the main objective, the energy policies should be designed in order to assure a deep and balanced penetration of the clean technologies, regardless of their estimated transitory impact on wholesale prices (and in the meantime reviewing the organisation of power markets).