In order to handle the mismatch between photovoltaic (PV) electricity production and household electricity use, battery storage systems can be utilized. However, the profitability of PV-battery systems in Sweden is poor, and economic incentives for households to invest in such systems are therefore missing. Hence, it is important to improve the profitability to increase the number of PV-battery installations. The aim of this thesis is to investigate the techno-economic potential of a PV-battery system offering ancillary services, more specifically the primary frequency regulation FCR-N. Five cases of residential PV-battery installations are investigated: the first with a PV system only, the second with a PV-battery system to store surplus PV electricity, and the three other cases with PV-battery systems with the ability to regulate the grid through FCR-N to varying degrees. The results show that providing FCR-N with a PV-battery system offers a substantial techno-economic potential for the system owner. By using available battery capacity for FCR-N, the payback time for a PV-battery system can be shortened significantly. With a battery price of EUR 570 per kWh (VAT excluded) and a discount rate of 2%, the payback time for the entire system can decrease from 32 to 9 years if the battery is used for FCR-N regulation. Furthermore, the payback time for a battery storage can be shortened with FCR-N. Calculated with respect to the economic added value of a battery and with a discount rate of 5%, the payback time can decrease from over 100 years to 4 years.