The case study described here concerns an HDR system which provides geothermal fluids for a hypothetical electric plant located in the Fenton Hill area in New Mexico's Jemez Mountains. Primary concern is focused on the implications of differing drilling conditions, as reflected by costs, and differing risk environments for the potential commercialization of an HDR system. Drilling costs for best, medium and worst drilling conditions are taken from a recent study of drilling costs for HDR systems. Differing risk environments are represented by differing rate-of-return requirements on stocks and interest on bonds which the HDR system is assumed to pay; rate of return/interest combinations considered are 6%/3%, 9%/6%, 12%/9% and 15%/12%. The method of analysis used here is that of determining the minimum busbar cost for electricity for this case study wherein all costs are expressed in annual equivalent terms. The minimum cost design for the electric generating plant is determined jointly with the minimum cost design for the HDR system. The interdependence between minimum cost designs for the plant and HDR system is given specific attention; the optimum design temperature for the plant is shown here to be lower than one might expect for conventional power plants - in the range 225/sup 0/ to 265/sup 0/C. Major results from the analyses of HDR-produced electricity in the Fenton Hill area are as follows. With real, inflation-free debt/equity rates of 6% and 9%, respectively, the minimum busbar cost is shown to lie in the range 18 to 29 mills/kwh. When real debt/equity rates rise to 12% and 15%, busbar costs rise to 24 to 39 mills/kwh.; DOE/ET/27017-T1