The massive increase in stochastic renewable generation, expected in the context of the energy transition, poses challenges to the stability of the power grid. Battery energy storage can positively impact the penetration of distributed solar photovoltaic (PV) systems while positively impacting the whole grid's hosting capacity in two different ways. First, it increases the amount of PV self-consumption and, therefore, increases the value of PV generation for prosumers. Second, batteries can provide ancillary services with particular value to frequency control. In this study, we analyze the techno-economic benefits and trade-offs for the prosumer and the grid associated with a pool of distributed storage systems, managed by an aggregator participating in the Swiss frequency control market. To this end, we apply a dispatch model to behind-the-meter batteries to quantify the added value of providing automatic and manual frequency restoration reserve (aFRR and mFRR) for prosumers. We find that the provision of aFRR and mFRR considerably increases the attractiveness of battery investments, in particular for large assets. However, the use of batteries for aFRR and mFRR brings along a reduction in total PV self-sufficiency, as well as a reduced battery lifetime, which should be taken into account by the prosumer at the moment of joining an aggregator, highlighting the duality between the prosumer's self-sufficiency and financial revenue.