Economic efficiency of rooftop photovoltaic systems. A differentiated view of full feed-in and self-consumption systems

Feed-in tariffs for rooftop photovoltaic systems have declined considerably in recent years, while the decrease in costs for installing systems has flattened out significantly. As a result, it is now only possible to operate PV systems up to 100 kWp economically if part of the electricity can be consumed by owners themselves. If the uneven development of feed-in tariffs and costs is not counteracted, many of the systems examined will no longer be economically viable until mid-2022, even with self-consumption. This results in a need to adjust the degression mechanism as compared to its previous core function (capping costs) such that it ensures a high level of new PV systems to be installed. In addition to the adjustment of the degression mechanism, a surcharge on feed-in tariffs would have to be implemented so that PV systems without self-consumption can also contribute to the required expansion. Homeowners and installers should no longer design PV systems according to the proportion of self-consumption, but according to the available roof potential so that this is fully utilised. Overall, the focus should be placed more on the contribution to decarbonisation of the entire electricity system and less on one's own house as a self-contained electricity cosmos.