There is an interesting technical side-argument here regarding the de-optimisation of the residual system. If VREs had to earn their revenue on the market rather than receive fixed remuneration, the revenue they would earn would be lower than the average of all the prices during the 8 760 hours of the year. This is because VRE production is self-correlated and concentrated during a limited number of hours of the year during which processes are particularly low, precisely because of high VRE production. Since this effect is precisely proportional to the variability of the VREs, the negative externality of system de-optimisation would, in fact, be directly internalised through the price system (see NEA, 2012a). However, as long as VRE receive fixed FITs, which protect them against this effect, the system de-optimisation due to over-deployment of VREs, from the point of view of economic efficiency, continues to impose an uninternalised social cost or “technical externality” on the electricity system. While they can impose highly unwelcome impacts on certain parties, e.g. traditional utilities, which may raise issues from a distributional or political point of view, they do not as such constitute social costs and rationales for public intervention.