The specific cost and parasitic load fraction are regressed of the form of Equation , where a, b, c, and d are the regression coefficients. The cost and load fraction is a function of ambient temperature ( ) (given in K), approach temperature difference (∆ ), and temperature range (∆ ). The approach temperature difference is the difference between the fluid temperature leaving the tower and the ambient temperature. The temperature range is the difference between inlet and exit fluid temperature. For a condensing tower, the range is zero.