Low-global warming potential (GWP) refrigerants are increasingly used in commercial refrigeration, but their real-world performance can differ significantly from theoretical expectations due to system design and safety constraints. This study compares R-717 and R-1234ze(E) chiller systems operating in a large cold storage facility, based on field measurements collected from March to June under varying seasonal and load conditions. Large-scale R-717 systems are typically designed in water-to-water configurations to limit refrigerant charge and leakage risks, in line with safety regulations. However, this approach introduces additional heat exchange stages, pumping energy, and temperature lifts, reducing overall system efficiency compared to ideal R-717 cycle performance. By contrast, R-1 ...