Geothermal Project Phases

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Geothermal Project Phases describe the level of progress for geothermal power projects under development, and are a property when defining geothermal developing projects. Geothermal development phases are reported by agencies to distinguish between the maturity of a geothermal project. Typically each agency updates their reports on an annual basis. Each agency that reports a development phase breaks up the development between early prospecting up to power plant commissioning. Due to the complexity of geothermal development, there are many different levels of detail that an agency could implement. Definitions from two reporting agencies, the Geothermal Energy Association (GEA) and SNL Financial (SNL), were used as guidelines to develop the OpenEI defintion of geothermal project phase below for geothermal developing project status. OpenEI users are encouraged to use the OpenEI designations when adding or updating a new or existing geothermal project.

OpenEI supports collaboration between industry, government agencies, and other outside parties. Changes that are made due to new information, and/or when existing information is deemed unreliable are strongly encouraged.


The Geothermal Energy Association (GEA) and SNL Financial (SNL) define different phases of a geothermal power project.

There are 4 GEA_Development_Phases as listed below:


SNL also utilizes 4 different development phases:

  • Announced – Starts when a project has been publicly announced.
  • Early Development – This is initiated once the permitting process has begun.
  • Advanced Development – 2 of the following 5 criteria must be achieved
    • Financing in Place
    • Power Purchase Agreement signed
    • Turbines Secured
    • Required Permits Approved
    • Contractor Signed onto the project
  • Construction begun – Construction of the project must have begun. Site Preparation is not considered project construction


While GEA and SNL both have similar definitions for geothermal development, there are some differences. SNL’s definitions are based upon the level of exploration, drilling, and construction that has been done at a particular site. GEA considers those criteria as well as adding transmission line planning, and how far along the project is in obtaining a power purchase agreement (PPA). In order to compare all of the developing projects against each other without misinterpreting GEA’s or SNL’s criteria, a third set of development phases has been developed for use in OpenEI. The relationship between the OpenEI, GEA, and SNL development status designations is defined below:

  • Unconfirmed – Not enough information to determine (GEA designation).
  • Early Exploration – Early stages of exploration and permitting such as site mapping, remote sensing, geochemistry, and other inexpensive exploration techniques.
  • Advanced Exploration – Exploration techniques such as geophysics, and thermal mapping through thermal gradient holes. This stage of exploration is aimed at determining where to design and build a reservoir.
  • Advanced Resource Development – Typically drilling techniques such as slim holes down to reservoir depth, full size production and injection wells, and well stimulation techniques.
  • Under Construction – Construction has begun, and major components such as turbine, cooling towers, pumps have been acquired.

The relationship between the OpenEI, GEA, and SNL development status designations is shown in the following table. OpenEI users are encouraged to use the OpenEI designations. If SNL or GEA designations are available this table can be referenced. This table is not intended to compare SNL vs GEA designations.

OpenEI Designation GEA Designation SNL Designation
Unconfirmed Unconfirmed N/A
Early Exploration Prospect, Phase I Announced
Advanced Exploration Phase II Early Development
Advanced Resource Development Phase III Advanced Development
Under Construction Phase IV Under Construction