The main objective of this study is to assess the potential for energy savings in the cooling water circuit of a vessel through the use of variable speed drives (VSDs). A small-scale cooling system was set up in the laboratory and relevant tests were carried out by simulating field conditions. Moreover, the payback period from VSDs installation on an existing 8000 TEU container ship based on the operational scenario of a representative journey was calculated. The result of the analysis revealed significant savings with a payback period of only a few months forVSD-controlled sea water pumps of a container vessel.