This paper analyses residential PV battery systems in order to gain insights into their sizing. For this purpose a simulation model was developed and system simulations on a timescale of one minute were performed. Furthermore, a sensitivity analysis was conducted varying the PV system and battery size to identify appropriate system configurations. Based on the simulation results, an economic assessment of PV battery systems was carried out and the cost-optimal configurations for various cost scenarios were determined. The results show that in the considered long-term scenario the conjunction of PV systems with batteries will be not only profitable but also the most economical solution.

• The performance of residential PV battery systems is evaluated using two primary metrics: the self-consumption rate and the degree of self-sufficiency.
• For achieving a high degree of self-sufficiency, a suitable system configuration is approximately 1 kWh of usable battery capacity for every 1 kWp of installed PV system power.
• As PV system size increases, the self-consumption rate tends to decrease, while the degree of self-sufficiency increases⁸. Increasing the battery size generally raises both metrics.
• The orientation of the PV generator (e.g., south-facing vs. east-facing) was found to have no major impact on the degree of self-sufficiency for the household load profile considered.
• Economic analysis shows that in a long-term scenario with falling costs, combining a PV system with a battery will not only be profitable but will represent the most economical solution for homeowners.