Geothermal Drilling Risk-Adjusted Cost Calculator
Comparing raw drilling cost across prospective geothermal sites can be misleading -- what actually matters is cost per MW after accounting for each site's exploration risk. This calculator produces a risk-adjusted cost-per-MW metric for comparing prospective sites or projects at different exploration confidence levels, making it a decision-support tool for early-stage site screening rather than program-level budgeting. It takes a site risk category (which auto-fills a representative well success rate), the cost per well, and the expected output per successful well, then reports the risk-adjusted cost per well and the risk-adjusted cost per MW. It is distinct from our Enhanced Geothermal System (EGS) Well Cost Calculator, which computes total drilling program cost for a target number of successful wells, and it pairs naturally with our Geothermal LCOE Calculator for the full levelized-cost picture that builds on these drilling economics.
Selecting a category auto-fills the well success rate below (still editable). Confirmed-resource sites sit adjacent to or within an existing producing field; appraisal-stage sites have some exploratory data but no producing wells yet; greenfield sites rely primarily on regional geologic indicators.
Success rate varies significantly with subsurface data quality -- a site adjacent to an existing producing field carries far less risk than a greenfield site with limited prior exploration.
Fervo Energy has demonstrated reducing EGS well drilling costs to roughly $4.8 million per well at its Cape Station project through drilling efficiency improvements.
Modern high-productivity EGS wells have demonstrated over 10 MW per well; conventional geothermal wells historically averaged closer to 3-5 MW per well.
cost per well ($) ÷ (well success rate (%) ÷ 100)
risk-adjusted cost per well ($) ÷ expected output per successful well (MW)
This calculator produces a planning-level risk-adjusted cost-per-MW metric for early-stage site screening and comparison, not a project budget. Actual well success rates depend on site-specific subsurface characterization, drilling and stimulation design, and operator experience, and actual output per successful well varies meaningfully well-to-well. Consult a qualified reservoir engineer and geoscientist for site-specific risk assessment before capital allocation decisions.
Results update live as you type. For planning and field-check estimates — always verify against applicable standards and equipment ratings.
How we calculate this →Comparing raw drilling cost across prospective sites can be misleading -- what actually matters is cost per MW after accounting for each site's exploration risk. An appraisal-stage site with a 75% success rate produces a risk-adjusted cost of $640,000/MW in this example, while the same well economics at a confirmed-resource site (90% success rate) would produce a meaningfully lower risk-adjusted cost per MW, and a greenfield exploration site (50% success rate) a meaningfully higher one. This is exactly why experienced geothermal developers weight site selection heavily toward confirmed or appraisal-stage resources rather than pure greenfield exploration wherever possible -- the drilling cost itself is often the smaller variable compared to the risk of an unsuccessful well.
How geothermal drilling risk-adjusted cost is calculated
This calculator produces a risk-adjusted cost-per-MW metric for comparing prospective geothermal sites or projects at different exploration confidence levels. It is a decision-support tool for early-stage site screening, distinct from the site's Enhanced Geothermal System (EGS) Well Cost Calculator, which computes total drilling program cost for a target number of successful wells. Two quantities tie the calculation together.
Risk-Adjusted Cost per Well ($) = Cost per Well ($) ÷ (Well Success Rate (%) ÷ 100). Dividing the per-well drilling cost by the success rate expressed as a fraction grosses up the cost to account for the wells that will be drilled but not succeed -- at a 75% success rate, each successful well effectively requires 1 / 0.75 = 1.33 wells of total drilling spend. At the defaults ($4,800,000 per well and 75% success rate), that is $4,800,000 ÷ 0.75 = $6,400,000.
Risk-Adjusted Cost per MW ($/MW) = Risk-Adjusted Cost per Well ($) ÷ Expected Output per Successful Well (MW). Dividing the risk-adjusted per-well cost by the electrical output each successful well delivers expresses the drilling risk in the unit that actually matters for site comparison -- dollars per MW of developable capacity. At the defaults ($6,400,000 risk-adjusted per well and 10 MW per successful well), that is $6,400,000 ÷ 10 = $640,000/MW.
Two notes on the model. First, the well success rate and the expected output per successful well are both planning-level inputs that vary significantly with subsurface data quality, drilling and stimulation design, and operator experience -- the site risk category dropdown auto-fills a representative success rate (90% for confirmed-resource sites adjacent to an existing producing field, 75% for appraisal-stage sites with some exploratory data, and 50% for greenfield sites with limited data), but the field remains editable so a site-specific figure can be substituted. Second, this metric is a comparison input for early-stage site screening and capital allocation, not a standalone go/no-go answer -- greenfield exploration is how new geothermal resource areas get discovered, and developers often pursue higher-risk sites deliberately as part of a portfolio strategy, understanding that early wells de-risk the resource for subsequent, cheaper development. For total drilling program budgeting at a target capacity, see the Enhanced Geothermal System (EGS) Well Cost Calculator; for the full levelized cost of energy that builds on these drilling economics, see the Geothermal LCOE Calculator. Data sources: EGS well drilling cost ($4.8M/well at Fervo Energy's Cape Station project) from Fervo Energy public reporting; modern EGS per-well productivity (10+ MW/well) and conventional geothermal per-well productivity (3-5 MW/well) from DOE (Department of Energy), NREL (National Renewable Energy Laboratory), and EIA (U.S. Energy Information Administration) geothermal performance data; representative well success rates by exploration stage from DOE Geothermal Technologies Office and industry geothermal exploration risk literature. Verification: with defaults (Appraisal Stage/75% success rate, $4,800,000/well, 10 MW/well), Risk-Adjusted Cost per Well = $6,400,000, Risk-Adjusted Cost per MW = $640,000/MW.