Abstract
Germany's ambitious energy transition, the Energiewende, is undergoing a critical shift as historical, high-rate Feed-in Tariffs (FiTs) for residential solar photovoltaic (PV) systems expire and new installations receive significantly lower tariffs. This policy transition shifts the economic incentive for households from grid-feeding to self-consumption, driving rapid interest in residential Battery Energy Storage Systems (BESS). This study presents an empirical agent-based model (ABM) to simulate the diffusion of coupled PV-BESS systems among German homeowners from 2024 to 2035 under various transitioning policy and market scenarios. The model integrates heterogeneous household agents characterized by economic constraints, environmental values, and localized social networks that facilitate peer-to-peer influence. Our findings indicate that while direct capital subsidies for batteries trigger immediate, short-term adoption spikes, they suffer from substantial free-rider effects. Conversely, rising retail electricity prices combined with declining battery costs serve as the primary long-term drivers of sustained BESS adoption. The results also highlight a widening disparity in energy autonomy between high-income property owners and low-income tenants, posing challenges for equitable grid fee distribution. Ultimately, our simulation suggests that policy frameworks must shift from simple technology-adoption subsidies toward dynamic, grid-supportive tariff structures to prevent grid defection while ensuring systemic stability.
