In the recent years photovoltaic installations have been growing rapidly both in numbers and in size. The main reason for this growth has been the generous subsidies offered by policy makers. As financial incentives are now being gradually removed, PV plant manufacturers are in quest for more efficient plant configurations that eventually reduce the investment cost and increase the annual energy yield. This paper presents a methodology for optimally sizing the PV panel strings (series-parallel connection of PV generators) for any specific inverter equipment and for a given location weather dataset. The methodology is based on some new PV plant performance metrics presented here. Finally, the concept of maximum power point of the inverter (MPPTi) is introduced.