U.S. Energy Information Administration - EIA - Independent Statistics and Analysis
Analysis & Projections
Assumptions to AEO2013
Release Date: May 14, 2013 | Next Release Date: May 2014 | full report
This report presents the major assumptions of the National Energy Modeling System (NEMS) used to generate the projections in the Annual Energy Outlook 2013  (AEO2013), including general features of the model structure, assumptions concerning energy markets, and the key input data and parameters that are the most significant in formulating the model results. Detailed documentation of the modeling system is available in a series of documentation reports .
The National Energy Modeling System
Projections in the AEO2013 are generated using the NEMS, developed and maintained by the Office of Energy Analysis of the U.S. Energy Information Administration (EIA). In addition to its use in developing the Annual Energy Outlook (AEO) projections, NEMS is also used to complete analytical studies for the U.S. Congress, the Executive Office of the President, other offices within the U.S. Department of Energy, and other Federal agencies. NEMS is also used by other nongovernment groups, such as the Electric Power Research Institute, Duke University, and Georgia Institute of Technology. In addition, the AEO projections are used by analysts and planners in other government agencies and nongovernment organizations.
The projections in NEMS are developed with the use of a market-based approach, subject to regulations and standards. For each fuel and consuming sector, NEMS balances energy supply and demand, accounting for economic competition among the various energy fuels and sources. The time horizon of NEMS extends to 2040. To represent regional differences in energy markets, the component modules of NEMS function at the regional level: the 9 Census divisions for the end-use demand modules; production regions specific to oil, natural gas, and coal supply and distribution; 22 regions and subregions of the North American Electric Reliability Corporation for electricity; and 8 refining regions that are a subset of the 5 Petroleum Administration for Defense Districts (PADDs). Maps illustrating the regional formats used in each module are included in this report. Only selected regional results are presented in AEO2013, which predominantly focus on the national results. Complete regional and detailed results are available on the EIA Analyses and Projections Home Page (www.eia.gov/analysis/).
NEMS is organized and implemented as a modular system (Figure 1). The modules represent each of the fuel supply markets, conversion sectors, and end-use consumption sectors of the energy system. The modular design also permits the use of the methodology and level of detail most appropriate for each energy sector. NEMS executes each of the component modules to solve for prices of energy delivered to end users and the quantities consumed, by product, region, and sector. The delivered fuel prices encompass all the activities necessary to produce, import, and transport fuels to end users. The information flows also include other data on such areas as economic activity, domestic production, and international petroleum supply. NEMS calls each supply, conversion, and end-use demand module in sequence until the delivered prices of energy and the quantities demanded have converged within tolerance, thus achieving an economic equilibrium of supply and demand in the consuming sectors. A solution is reached for each year from 2012 through 2040. Other variables, such as petroleum product imports, crude oil imports, and several macroeconomic indicators, also are evaluated for convergence. Each NEMS component represents the impacts and costs of legislation and environmental regulations that affect that sector. NEMS accounts for all combustion-related carbon dioxide (CO2) emissions, as well as emissions of sulfur dioxide (SO2), nitrogen oxides (NOx), and mercury from the electricity generation sector.
The integrating module of NEMS controls the execution of each of the component modules. To facilitate modularity, the components do not pass information to each other directly but communicate through a central data storage location. This modular design provides the capability to execute modules individually, thus allowing decentralized development of the system and independent analysis and testing of individual modules. This modularity allows use of the methodology and level of detail most appropriate for each energy sector. NEMS solves by calling each supply, conversion, and end-use demand module in sequence until the delivered prices of energy and the quantities demanded have converged within tolerance, thus achieving an economic equilibrium of supply and demand in the consuming sectors. Solution is reached annually through the projection horizon. Other variables are also evaluated for convergence such as petroleum product imports, crude oil imports, and several macroeconomic indicators. The version of NEMS used for AEO2013 generally represents current legislation and environmental regulations, including recent government actions for which implementing regulations were available as of September 30, 2012, such as: the new light-duty vehicle (LDV) greenhouse gas (GHG) and corporate average fuel economy (CAFE) standards for model years 2017 to 2025 released in October 2012; the Clean Air Interstate Rule (CAIR), which was reinstated as binding legislation after the Cross- State Air Pollution Rule (CSAPR)  was vacated on August 21, 2012; updated handling of the U.S. Environmental Protection Agency's (EPA) National Emissions Standards for Hazardous Air Pollutants for industrial boilers and process heaters  based on regulations released in March 2011; the Mercury and Air Toxics Standards  issued by the EPA in December 2011; California's cap-and-trade program authorized by Assembly Bill 32 (AB 32), the Global Warming Solutions Act of 2006 , issued in September 2006; and the California Low Carbon Fuel Standard (LCFS)  finalized in January 2010.
The potential impacts of proposed federal and state legislation, regulations, or standards—or of sections of legislation that have been enacted but require funds or implementing regulations that have not been provided or specified—are not reflected in NEMS. Many of the pending provisions, however, are examined in alternative cases included in AEO2013 or in other analysis completed by EIA. A list of the specific federal and selected state legislation and regulations included in the AEO, including how they are incorporated, is provided in Appendix A.
Footnotes Energy Information Administration, Annual Energy Outlook 2013 (AEO2013), DOE/EIA-0383(2013), (Washington, DC, April 2013).
 NEMS documentation reports are available on the EIA Homepage (www.eia.gov/analysis/model-documentation.cfm).
 U.S. Environmental Protection Agency and National Highway Traffic Safety Administration, "2017 and Later Model Year Light- Duty Vehicle Greenhouse Gas Emissions and Corporate Average Fuel Economy Standards," Federal Register, Vol. 77, No. 199, 40 CFR Parts 85, 86, and 600, and 49 CFR Parts 523, 531, 533, et al. (Washington, DC: October 15, 2012), website www. gpo. gov/fdsys/pkg/FR-2012-10-15/html/2012-21972.htm.
 U.S. Environmental Protection Agency, "Cross-State Air Pollution Rule (CSAPR)" (Washington, DC: January 14, 2013), website http://epa.gov/airtransport. CSAPR was scheduled to begin on January 1, 2012; however, the U.S. Court of Appeals for the D.C. Circuit issued a stay delaying implementation while it addresses legal challenges to the rule that have been raised by several power companies and States. CSAPR is included in AEO2013 despite the stay, because the Court of Appeals had not made a final ruling at the time AEO2013 was published.
 U.S. Congress, "Clean Air Act: Chapter 85—Air Pollution Prevention and Control," 42 U.S.C. 7412 (2011), website www.gpo.gov/fdsys/pkg/USCODE-2011-title42/pdf/USCODE-2011-title42-chap85.pdf.
 U.S. Environmental Protection Agency, "Mercury and Air Toxics Standards (MATS)" (Washington, DC: March 27, 2012),website www.epa.gov/mats.
 California Environmental Protection Agency, Air Resources Board, "Assembly Bill No. 32: Global Warming Solutions Act" (Sacramento, CA: September 27, 2006), website www.arb.ca.gov/cc/ab32/ab32.htm.
 California Environmental Protection Agency, Air Resources Board, "Low Carbon Fuel Standard Program" (Sacramento, CA: January 11, 2013), website www.arb.ca.gov/fuels/lcfs/lcfs.htm. U.S. Environmental Protection Agency, "Mercury and Air Toxics Standards," website www.epa.gov/mats.
Sections by Module
Macroeconomic Activity Module
International Energy Module
Residential Demand Module
Commercial Demand Module
Industrial Demand Module
Transportation Demand Module
Electricity Market Module
Oil and Gas Supply Module
Natural Gas Transmission and Distribution Module
Liquid Fuels Market Module
Coal Market Module
Renewable Fuels Module
Appendix A: Handling of Federal and selected State legislation and regulation in the AEO