Thermodynamic heat pumps are central to modern energy-efficient heating and cooling across residential, commercial, and industrial sectors. By transferring heat instead of generating it, they achieve significantly higher efficiency than conventional systems. A critical yet often overlooked factor influencing performance is the choice of refrigerant. Acting as the working fluid, the refrigerant governs how effectively heat is absorbed, compressed, and released throughout the cycle. Its physical and chemical properties directly impact efficiency, reliability, and durability. As sustainability becomes a priority, selecting the right refrigerant is essential not only for optimal system performance but also for minimizing environmental impact and ensuring long-term operational efficiency.