Geothermal Power Plant Output Calculator
This calculator sizes a geothermal power plant from the wellfield up: it takes the number of production wells and the average electrical output per well to get gross plant capacity, then applies a capacity factor across 8,760 hours to report annual energy output in MWh/year. At modern Enhanced Geothermal System (EGS) well productivity -- demonstrated by Fervo Energy's Cape Station project at roughly 10 MW per well -- 40 wells nets 400 MW of gross capacity and over 3.1 million MWh/year, the real scale of utility EGS projects now under development. It pairs naturally with our Geothermal Capacity Factor Calculator for the capacity-factor side of the same calculation, and our Enhanced Geothermal System (EGS) Well Cost Calculator for the drilling cost of building that wellfield.
The number of commercially productive production wells feeding the plant. Forty wells is representative of a large modern EGS project like Fervo Energy's Cape Station.
Fervo Energy's Cape Station project has demonstrated initial well tests exceeding 10 MW per well using Enhanced Geothermal System (EGS) horizontal drilling -- a major improvement over the historical industry average of roughly 3-5 MW per well for conventional flash and binary geothermal wells.
Geothermal plants typically achieve 85-95%+ capacity factor, among the highest of any generation source, since geothermal resources produce continuously with only scheduled maintenance downtime.
number of production wells × average output per well (MW)
gross plant capacity (MW) × 8,760 × (plant capacity factor (%) ÷ 100)
This calculator sizes gross plant output from well count and average per-well productivity at a planning level. Actual plant output depends on well-to-well productivity variation, reservoir temperature and flow over time, surface plant conversion efficiency, and parasitic loads; gross capacity also differs from net sellable capacity after station service and auxiliary equipment. Consult a qualified reservoir and power-plant engineer for project-specific sizing.
Results update live as you type. For planning and field-check estimates — always verify against applicable standards and equipment ratings.
How we calculate this →Modern EGS well productivity has changed geothermal project economics dramatically -- 40 wells at 10 MW each nets 400 MW of gross capacity, matching the real scale of Fervo Energy's Cape Station project in Utah, which is targeting 400 MW by 2028 for customers including Southern California Edison. That's a meaningful jump from the 3-5 MW per well historically typical of conventional geothermal, meaning modern EGS projects can reach utility-scale capacity with far fewer wells than earlier geothermal technology required.
How geothermal power plant output is calculated
This calculator sizes a geothermal power plant from the wellfield up by first multiplying the number of production wells by the average electrical output per well to get gross plant capacity, then applying a capacity factor across a full year to report annual energy output. Two quantities tie the calculation together.
Gross Plant Capacity (MW) = Number of Production Wells × Average Output per Well (MW). Each production well contributes its average electrical output to the plant's total, so multiplying the well count by the per-well output gives the plant's gross nameplate capacity. At the defaults (40 wells and 10 MW/well), that is 40 × 10 = 400 MW.
Annual Energy Output (MWh/year) = Gross Plant Capacity (MW) × 8,760 × (Plant Capacity Factor (%) ÷ 100). Gross capacity in MW multiplied by 8,760 hours gives the energy the plant would produce running at full output all year, and multiplying by the capacity factor expressed as a fraction scales that theoretical maximum down to what the plant actually generates given maintenance, outages, and reservoir conditions. At the defaults (400 MW and 90% capacity factor), that is 400 × 8,760 × 0.90 = 3,153,600 MWh/year.
Two notes on the model. First, the average output per well is the single most consequential input alongside well count, and it is applied as a single average across all wells -- real wellfields see meaningful well-to-well productivity variation, and EGS well productivity has improved substantially in recent years as horizontal drilling and stimulation techniques borrowed from the oil and gas industry have matured, so the editable field lets you substitute a project-specific or area-specific figure. Second, this calculator reports gross plant capacity and gross annual energy output; it does not model net sellable capacity after parasitic loads (station service and auxiliary equipment), surface plant conversion efficiency differences between flash steam and binary cycle plants, or reservoir pressure and temperature decline over the project life, all of which a full project model would include. For the capacity-factor side of this same calculation, see the Geothermal Capacity Factor Calculator; for the drilling cost of building this wellfield, see the Enhanced Geothermal System (EGS) Well Cost Calculator. Data sources: EGS per-well productivity (10+ MW/well at Fervo Energy's Cape Station project) and Cape Station 400 MW by 2028 target from Fervo Energy public reporting and Southern California Edison power purchase agreement disclosures; conventional geothermal per-well productivity (3-5 MW/well) and geothermal capacity factor ranges (85-95%+) from DOE (Department of Energy), NREL (National Renewable Energy Laboratory), and EIA (U.S. Energy Information Administration) geothermal plant performance data. Verification: with defaults (40 wells, 10 MW/well, 90% capacity factor), Gross Plant Capacity = 400 MW, Annual Energy Output = 3,153,600 MWh/year.