Photovoltaics (PV)-coupled battery energy storage systems (BESSs) are becoming more popular due to the reduction of BESS costs as well as the decreased remuneration of PV grid injection over the last few years. This paper compares the techno-economic system performance of two sizing approaches of PV-coupled BESSs - using mixed integer linear programming - for a case study in the Netherlands. The first approach uses a static sizing methodology to size the BESS based on the daily PV grid injection. While the second approach considers the BESS energy and power capacity as decision variables in an optimization problem to optimally size the BESS. The results demonstrate that the total costs can be reduced by 41% with our second approach - when the BESS is optimally sized considering annual demand and generation profiles.