Emissions Policy Module - NEMS Documentation
July 2025
Introduction
EPM is the Emissions Policy Module of the National Energy Modeling System (NEMS). The main purpose of the EPM is to handle calculations of energy-related carbon dioxide (CO2) emissions at the U.S. economic sector and regional levels. These calculations are performed using energy consumption estimates (which vary by sector, region, and year) and applying applying appropriate sector-by-fuel emissions factors (which are established using the latest historical data and are static over the projection). In addition to providing projections of CO2 emissions, the EPM is also responsible for implementing various CO2 policy evaluation options. These options can be used to simulate proposed market-based approaches to meet national CO2 emission objectives.
The CO2 emissions estimates and policies modeled by the EPM focus specifically on energy- related CO2 emissions. We define energy-related CO2 emissions as those resulting from fossil fuel combustion, released during non-fuel use of energy products (such as industrial feedstocks), and released during energy production (such as CO2 vented from geothermal wells). This distinction between energy- and non-energy CO2 emissions categories in NEMS is discussed further in the Model Assumptions section.