<p>Heat pump technology can effectively recover waste heat from low-grade wastewater, which is crucial for energy conservation and carbon emission reduction in buildings. When recovering waste heat via a heat pump, the evaporator requires a larger temperature difference between the inlet and outlet water, which can be improved using zeotropic mixtures to enhance temperature matching. Current research on the application of zeotropic mixtures for deep utilization of waste heat is relatively scarce. In this study, zeotropic mixtures with large glide temperature were applied in a heat pump water heater to realize deep utilization of waste heat. To investigate the energy-saving potential, a heat pump hot water system was built to test the performance of different low Global Warming Potential (GWP) zeotropic mixtures, including CO₂/R1234yf and CO₂/R290 mixtures. Additionally, pure R290 was used for comparison under identical conditions. The results indicate that the optimal charge amount for the CO₂/R1234yf and CO₂/R290 mixtures at different CO₂ mass fractions are 1.1&#xa0;kg and 0.6&#xa0;kg, respectively. Under the selected conditions, both the CO₂/R1234yf and CO₂/R290 mixtures exhibited an optimal heating Coefficient of Performance (COP_H) with a mass fraction of CO₂ of 15%. For CO₂/R290, the heat pump showed a 75.2% increase in COP_H and a corresponding 107.7% increase in the volumetric heating capacity (<i>q</i>_v) compared with pure R290. For CO₂/R1234yf, the heat pump exhibited a 27.7% increase in COP_H and a corresponding 92.0% increase in <i>q</i>_v compared with pure R290. These results provide a foundation for the design and application of CO₂ zeotropic mixture heat pumps based on the deep utilization of waste heat.</p>