Well stimulation cost is the cost of pressurizing the impermeable basement rock of a so-called Enhanced Geothermal System (EGS) reservoir to create artificial fractures through which heat can be extracted. Naturally permeable geothermal systems, such as those using porous reservoirs, do not require stimulation. When these typical, naturally permeable, geothermal resources are used, the stimulation cost is zero. Table shows a comparison of stimulation costs found in our literature review. The costs are inflated by the inverse of the success rate and do not include indirect costs and contingency. Figure shows O&M costs from several references for both geothermal systems and power cycle electricity generation systems in general. The average O&M cost fraction for each source is reported by the bar height. The geothermal community does not publish its cost figures readily, thus we have also included relevant related power cycles costs such as coal and natural gas electricity generators. The O&M cost fractions are also reported in Table .