This paper discusses the possibility to reduce the energy efficiency design index for ships through a post-combustion carbon capture process. The post-combustion carbon capture process, successfully implemented in the electricity generation sector, allows reduction of CO₂ emissions of existing units using fossil fuels with relative simplicity. An assessment of implementing an amine-based carbon capture system onboard of the ship is presented. The analysis covers the energy requirements of the entire system including SO₂ removal, carbon capture and CO₂ compression. Simulations, conducted for different ambient conditions, revealed that the highest CO₂ emission, translating into a reduction of the EEDI, is possible in tropical conditions. The energy efficiency reduction is possible also in arctic conditions to a lesser extent. The post-combustion carbon capture process seems to be a promising technology as the method to reduce the EEDI for ships. An additional advantage is the possibility to retrofit existing constructions as the implementation requires no significant changes in the ship propulsion system. Finally, the nature of the amine-based carbon capture process, aimed to remove acidic exhaust gas components, supports SO₂ emission reduction, making the exhaust gas practically sulfur-free.