The substantial growth in the number of ground-coupled systems and the innovative practices of some contractors have resulted in very low cost vertical installations. Cost per foot in the $5.00 or less range is not uncommon. Although there is some reduction in the unit cost per foot in larger installations, the cost of any installation is directly related to system capacity (tons) since a fixed number of feet per ton is required at a fixed cost per foot. The hybrid system results in a lower overall capital cost; but substitutes slightly increased operating costs from pump and fan electrical consumption and water treatment