Decentralized photovoltaic (PV) battery systems have recently received great attention from consumers around the world. PV battery systems allow consumers to reduce their dependence on the local electricity supplier at lower or equivalent costs. However, the profitability of PV battery systems depends greatly on the local meteorological conditions and the local electricity retail tariff. In central European countries, PV battery systems generate and store less electricity in winter months due to lower irradiation. The battery, in particular, can be reserved to provide ancillary services during winter months and thereby improves the overall systems economics. In this study, a large dataset consisting of individual load profiles is used to simulate a virtual power plant which provides ancillary services during battery idle times. The results show that participants with large batteries can greatly increase their overall systems economics by participating in reserve markets. However, participants with small battery capacities may not be able to recover the additional costs for communication with the virtual power plant and are thus not suitable candidates to provide grid stabilizing services (ancillary services).