Maritime shipping is a cornerstone of global commerce, enabling the transport of goods across continents and fueling economic development. However, its substantial dependence on fossil fuels positions it as a major source of CO2 emissions and environmental impact. This study assesses energy demands, CO2 emissions, and infrastructure for electrifying container ships across three size categories operating from Los Angeles Harbor (LAH). Findings indicate annual energy consumption of 227,842 MWh, 253,884 MWh, and 253,055 MWh, respectively, for each class. Notably, larger vessels achieve enhanced energy efficiency per TEU, with energy demand per TEU decreasing from 45.57 MW-hr/TEU for 5000–7999 TEU ships to 21.09 MW-hr/TEU for 12,000–14,499 TEU vessels. While smaller vessels maintain slightly higher average speeds (24.6 knots for 5000–7999 TEU ships compared to 23.8 knots for 12,000–14,499 TEU), larger ships offer superior sustainability in fuel efficiency and emissions per kilometer traveled. The analysis also shows that increased battery weight elevates power requirements, raising fuel use by 3% for the largest class. Transitioning to alternative fuels, such as Methanol, demonstrates the potential for substantial CO2 reductions, with emissions as low as 29.8 gCO2/TEU-mile for the largest vessels. Furthermore, California’s clean grid capacity analysis reveals that larger ships achieve maximum energy efficiency, up to 1015.85 kWh/km for the 8000–11,999 TEU class, highlighting the environmental and operational advantages of scaling vessel size in maritime transport.