 When compared, groundwater heat pumps are generally more efficient than heat pumps using heat from the soil.Closed loop soil or ground heat exchangers tend to accumulate cold if the ground loop is undersized.This can be a significant problem if nearby ground water is stagnant or the soil lacks thermal conductivity, and the overall system has been designed to be just big enough to handle a "typical worst case" cold spell, or is simply undersized for the load.