IM-GEO is an analysis used to estimate the impact of technology improvements on the relative cost of hydrothermal power. The analysis is available in a tutorial program for use on personal computers. It is designed for use by R and D program managers to evaluate R and D options. Only the potential impact of technologies is considered with all economic factors being held constant. This analysis has one unique feature. The economic impact of reducing risk by improving reservoir characterization is included using a strategy currently employed by financial institutions. This report describes the basis of the calculations, documents the code, and describes the operational procedures. Application of the code to study potential cost reductions due to R and D success will be done by R and D managers to evaluate and direct their own programs.