Electric vehicle (EV) transportation aboard RoPax vessels presents several technical, safety, and regulatory challenges that must be carefully addressed for effective implementation. This study investigates the integration of an EV charging facility on a RoPax vessel, focusing on its impact on operational carbon dioxide emissions and compliance with maritime energy efficiency regulations. Motivated by the need for sustainable maritime transport, the research aims to evaluate various battery charging configurations for 200 EVs, assessing the total electrical energy required and the additional loads on the ship's electrical system. A scenario-based analysis is conducted using three engine configurations powered by different marine fuels. Key findings reveal a carbon intensity variation of up to 5.3% based on fuel choice during an eight-hour round-trip voyage. The dual-fuel engine using liquefied natural gas meets Energy Efficiency Existing Index (EEXI) requirements, achieving an 8.121 Carbon Intensity Indicator (CII) value without charging, thus ensuring an A rating until 2026. Even in the worst-case charging scenario, the carbon intensity of this configuration increases by only 2.26%, still complying with EEXI and CII metrics. This research offers a comprehensive evaluation of EV charging impacts on RoPax vessels, providing insights for adapting and optimizing ship power systems.