How much energy autonomy can decentralised photovoltaic generation provide? A case study for Southern Germany

Energy autonomy, the desire to become independent from a centralised supply system, is a core motivation for the development of decentralised energy systems, even if it does not have tangible economic or ecological benefits. For the case of electricity, we introduce a regional system model which optimises the capacity expansion and operation of photovoltaics and battery storage. We quantify cost-efficient regional degrees of electricity autonomy for 166 regions in Southern Germany and assess how increasing the degree of autonomy beyond the optimal level affects the economic viability of a decentralised electricity system. We find that the average optimal degree of autonomy reached is 44%. Thus, our results show that a substantial increase of photovoltaic capacity is economically beneficial in all the regions examined. However, achieving a predefined degree of autonomy causes additional costs for the region and results in a large overcapacity, while all regions still rely on the superordinate electricity system to some extent.