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Integrating Module - NEMS Documentation

July 2022


The National Energy Modeling System (NEMS) is an energy-economy modeling system of U.S. energy markets for the midterm period, extending through 2050, which currently runs on Windows-based personal computers and terminal servers. NEMS projects the production, imports, conversion, consumption, and prices of energy, subject to a number of assumptions. The assumptions encompass macroeconomic and financial factors, world energy markets, resource availability and costs, behavioral and technological choice criteria, technology characteristics, and demographics. NEMS produces a general equilibrium solution for energy supply and demand in the U.S. energy markets on an annual basis.

Baseline projections from NEMS are published in the U.S. Energy Information Administration’s (EIA) Annual Energy Outlook. Our Office of Energy Analysis develops and maintains NEMS to project domestic energy-economy markets in the long term and analysts performs policy analyses requested by decision makers in the White House; the U.S. Congress; offices within the U.S. Department of Energy, including program offices; and other government agencies. NEMS was first used for projections presented in the Annual Energy Outlook 1994.

Scope and organization

Publication of this document is supported by Public Law 93-275, Federal Energy Administration Act of 1974, Section 57(B)(1) (as amended by Public Law 94-385, Energy Conservation and Production Act), which states in part

...that adequate documentation for all statistical and forecast reports prepared...is made available to the public at the time of publication of such reports.

In particular, this report meets EIA’s model documentation standard 2015-1, established under these laws.[1]

For documentation purposes, the individual components of NEMS are considered distinct models and documented individually. Although the NEMS Integrating Module is a distinct component of NEMS, the Integrating Module is not by itself a model. Rather, it is a component of the overall NEMS model and implements specific aspects of the overall modeling methodology that are not documented elsewhere. The documentation is organized accordingly.

Because the Integrating Module controls the solution process for all components of NEMS, Chapter 2 summarizes NEMS as a whole. Readers interested in a more comprehensive summary of NEMS should see The National Energy Modeling System: An Overview 2018, April 2019.[2]

Chapter 3 describes the NEMS global data structure, which is used for inter-module communication, solution initialization and storage, and certain database operations.

Chapter 4 provides the mathematical specification for the solution algorithm and describes the convergence techniques used. Chapter 4 also documents other modeling functions of the Integrating Module, including generation of foresight assumptions and carbon dioxide emission policy routines.

Appendix A is the bibliography, and Appendix B describes some of the configuration management and other implementation practices used to coordinate NEMS software development.

Model archival citation

This documentation refers to the NEMS Integrating Module as archived for the Annual Energy Outlook 2022 (AEO2022).

See full report

Notes and sources

[1]See https://www.eia.gov/about/eia_standards.php#standard2015_1.

][2See https://www.eia.gov/outlooks/aeo/nems/overview/pdf/0581(2018).pdf.