Geothermal systems generally refers to heating and cooling systems that pump energy out of or into the subsoil under and around a building. This amount of energy is pumped with the use of water/water pumps. These latter operate similarly to air/water pumps, only that in this case they take advantage of subsoil heat, which during winter preserves a temperature much higher than that of air, through a water pipes circuit. These circuits can be vertical or horizontal, closed or open to a sump of water. Geothermic pumps display a very high efficiency COP (coefficient of performance) as they take advantage of the subsoil which retains temperature stability at moderate grade levels throughout the year, approximately equal to the mean annual air temperature of the atmosphere. They are money-saving and environmentally friendly.