Technically, the thermodynamic principle is the same: a refrigerant changes state to transport heat. An air/air split, a reversible air/water heat pump and a ground-source heat pump all work this way; the difference lies in the cold or hot source (air, water, ground) and the refrigerant used. What changes the carbon footprint: equipment SEER, source stability and refrigerant GWP. Ground-source is the most efficient (SEER 5 to 8+, stable ground source at 12-14 °C even during heatwaves, low leak rates in a closed circuit) and the least emissions-intensive over 20 years, but costs €10,000 to €25,000 (including drilling) compared with €1,000 to €4,000 for a split. It suits new buildings, major renovations or long-term commercial use; in an existing home, low-energy measures (solar protection, ceiling fans, free cooling) remain the first measure.
Read the source article: What is the environmental impact of air conditioning?