The provision of chilled water is a critical service in any warship as it ensures mission systems can operate reliably within suitably air conditioned spaces. A Chilled Water Plant (CWP) cools circulating clean filtered water through a refrigeration system which passes the heat to sea water (SW). Historically, the refrigerant employed has been damaging to the Earth’s ozone layer but these were outlawed by the UN Montreal Protocol. Since then new refrigerants such as R134a have provided much improved ozone depletion but they have a high Global Warming Potential (GWP) if leaked to the atmosphere. To address the GWP issue, the European directive 2006/40/EC, which went into effect in 2011, required all new cars on sale in Europe to use a refrigerant in its air-conditioning system with a GWP below 150. One group of the new refrigerants to address this required change are called hydrofluoroolefins (HFO) with the R1234yf being a leading candidate for general use with a GWP of 4. However, R1234yf is currently manufactured in limited quantities and so is quite costly. It also has mild flammability with toxic products when combusted. Although it is a close drop-in for R134a, it requires changes to the lubricating oil. Paradoxically, carbon dioxide (CO₂) has long been used as a refrigerant and is often used for cold and freezer displays in shops. It is not flammable and has a GWP of 1, much lower than many alternative refrigerants. However with a critical point of 31°C and 71 bar, a CWP cooled by SW the refrigeration cycle would need to be transcritical, i.e. the use of CO₂ as a supercritical fluid. To obtain a rounded assessment of the benefit of CO₂, versus R134a, the performance of two indicative CWP designs has been analysed. The Coefficient of Performance (COP) and other design and performance issues are identified. The system arrangement and equipment selection issues are addressed, together with a high level consideration of the GWP in-service for different refrigerant leak/loss rates. The ability to drive an absorption chiller plant (ACP) with the heat rejected from the CO₂ CWP is assessed and the energy efficiency and ship cooling benefits are assessed.