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, A heat pump extracts heat from the home and transfers it to the cooler fluid, which is then dissipated into the ground. Geothermal HVAC is highly energy-efficient, although installation costs can be higher due to the ground loop installation. Geothermal systems reduce energy use and have a smaller carbon footprint.