Geothermal HVAC systems use the stable ground temperature as a heat exchange medium. A network of pipes (a ground loop) circulates fluid underground, absorbing heat from the earth in winter and transferring it into the building. In the summer, the process reverses, with the system transferring heat from the building to the ground. Geothermal HVAC is highly energy-efficient, although installation costs can be higher due to the ground loop installation. It's an environmentally friendly way to heat and cool your home or business.