This study introduces the updated version of the NTC 4405 standard, which was last revised in 1998 and no longer aligns with the modern equipment being used. Furthermore, it fails to address crucial stages, such as energy conversion and inversion. By thoroughly examining national and international regulations, a comprehensive methodology has been developed to accurately measure the total efficiency of off-grid solar photovoltaic systems. This methodology encompasses every stage of the system, including solar panels, charge controllers, battery banks, and power converters/inverters.