Free Online Geothermal Resource Calculator: Heat in Place to MWe

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The USGS volumetric method: heat in place is rock volume times volumetric heat capacity times the temperature above your reference. Recovery takes most of it away, conversion efficiency most of the rest, and dividing what survives by the project life gives the sustainable electric rating. For district heating, skip the conversion step and read the thermal number.

From hot rock to a megawatt rating

A geothermal prospect is a volume of hot rock, and the volumetric method turns it into a power rating in four honest steps: heat in place from volume, heat capacity, and temperature above your reference; a recovery factor for the fraction wells can actually sweep; a conversion efficiency for turning low-grade heat into electricity; and a project lifetime that spreads the recovered energy into a sustained megawatt figure. The tool above runs the whole cascade and reports each stage, so you can see exactly where the enormous initial number shrinks to the tens of megawatts that get financed.

Bar chart cascade from heat in place through recoverable heat and conversion efficiency down to the electric megawatt rating of a geothermal resource
The volumetric cascade: each step shrinks the number, and what survives over a project lifetime is the financeable rating.

This is the third tool in the CO2 Storage and Geothermal Suite. The same subsurface skills that find hydrocarbons, mapped volume, temperature, porosity, and permeability, price a geothermal resource.

The honest knobs

  • Recovery factor dominates the uncertainty: hydrothermal systems achieve 10 to 25 percent, enhanced geothermal far less so far, and the choice moves the answer more than any measurement.
  • Conversion efficiency is physics, not pessimism: binary plants at 150 to 200 degrees convert 10 to 13 percent of heat to electricity, set by thermodynamics.
  • The reference temperature matters: for power use the reinjection temperature, for district heating a much lower one, which is why heating projects extract several times more useful energy from the same rock.
  • The household figure uses a rough one megawatt per eight thousand homes; adjust mentally for your grid.

What this tool is for

Screening prospects, checking feasibility studies, and teaching the USGS volumetric method with every assumption exposed. Bankable assessments add reservoir simulation and drilling results; this cascade is the frame they all hang on.

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