Geothermal HVAC systems use the relatively constant temperature of the earth as a heat source in winter and a heat sink in summer. 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. It's an environmentally friendly way to heat and cool your home or business.