This paper examines hybrid ground-source and air-source heat pump systems through empirical data and presents the findings. 1) Geothermal-only systems lost rainwater tank cooling ability within 3 days, whereas hybrid systems stayed effective for 5 days. 2) Rainwater from a 5m-deep tank circulated through a radiator at the outdoor unit’s inlet, cooling air by 10°C and maintaining inlet temperatures at 24–31°C in summer. 3) Unlike constant-pumping geothermal systems, hybrid systems activate water flow only when outside temperatures exceed 30°C, significantly reducing pump runtime while ensuring rainwater in tanks is naturally cooled by the soil during idle periods.
