Geothermal HVAC systems use the relatively constant temperature of the earth as a heat source in winter and a heat sink in summer. During winter, heat from the ground warms the fluid, and this warmth is extracted by a heat pump and transferred indoors. 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.