Frequent Questions about eGRID
On this page:
- What is eGRID?
- Why eGRID?
- What information is contained in eGRID?
- Who uses eGRID?
- What years are available for eGRID?
- What has changed in recent years?
- What is new in eGRID2022?
- How do eGRID2022 subregion rates compare to eGRID2021?
- Are EIA-923 data updates reflected in eGRID?
- What eGRID data year should be used?
- Which geographic level of eGRID data should be used to determine emissions from electricity use?
- What are nonbaseload emission rates and when should they be used?
- What is Grid Gross Loss (GGL)?
- How has the methodology for assigning plants to eGRID subregions changed?
- How has the methodology for estimating methane (CH4) emissions changed?
- What are GWPs and which GWPs does eGRID use to calculate emissions?
- Did the eGRID naming convention change?
- Is there additional eGRID data available?
- What do the eGRID subregion and NERC region maps look like?
- How has the subregion map changed?
- What are the regional emission rates and resource mix?
- How can I receive eGRID related news from EPA?
- What other emissions data are available from EPA?
- Why are there outliers for some output emission rates?
- Why are there differences at a small number of plants between total net generation and generation by fuel type?
- What other EPA tools are available to estimate avoided emissions from EE/RE programs?
- Can I use eGRID data commercially and how do I cite it?
- How can I provide feedback or ask questions?
1) What is eGRID?
The Emissions & Generation Resource Integrated Database (eGRID) is a comprehensive inventory of environmental attributes of electric power systems. The preeminent source of air emission data for the electric power sector, eGRID is based on available plant-specific data for all U.S. electricity generating plants that provide power to the electric grid and report data to the U.S. government. eGRID uses data from the Energy Information Administration (EIA) Forms EIA-860 and EIA-923 and EPA’s Clean Air Power Sector Program Data. Emission data from EPA are carefully integrated with generation data from EIA to produce useful values like pounds of emissions per megawatt-hour of electricity generation (lb/MWh), which allows direct comparison of the environmental attributes of electricity generation. eGRID also provides aggregated data by state, U.S. total, and by three different sets of electric grid boundaries (i.e., balancing authority area, North American Electric Reliability Corporation (NERC) region, and eGRID subregion).
2) Why eGRID?
Many consumers have a choice regarding the source of their electricity, and some consumers seek cleaner sources, such as wind and solar power. EPA’s Power Profiler, which uses eGRID data, helps individual consumers understand the environmental impacts of their electricity usage.
Electricity generation is the dominant industrial source of air emissions in the United States. Whenever you switch on an electrical appliance, chances are you are contributing to air pollution and greenhouse gas emissions. By documenting the environmental attributes of electric power generation, eGRID can help consumers and researchers to better understand the relationship between electricity use and the environment.
In the United States, electricity is generated in many different ways, with a wide variation in environmental impacts. In many states, power companies are required to disclose the environmental attributes of their retail electricity products. eGRID data can be used to support the following activities:
- Greenhouse gas registries and inventories,
- Carbon footprinting of electricity purchases,
- Consumer information disclosure,
- Renewable portfolio standards,
- Development of emission inventories and emission standards,
- Analysis of changing power markets, and
- Estimation of avoided emissions.
3) What information is contained in eGRID?
For virtually every grid-connected power plant in the United States located at a facility with at least a 1 MW combined nameplate capacity, eGRID provides:
- A detailed emissions profile covering nitrogen oxides (NOX), sulfur dioxide (SO2), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), mercury (Hg), and partifculate matter (PM2.5).
- Mass emissions are reported in either pounds or tons.
- Output emission rates are reported in pounds per megawatt-hour (lb/MWh).
- Input emission rates are reported in pounds per million British thermal units (lb/MMBtu).
- Generation resource mix, in megawatt-hours and percent.
- Information identifying power plants, as well as their attributes and location.
eGRID provides separate data at the combustion unit and generator levels. These data are combined at the plant level. The plant level data are then aggregated to state, U.S. total, and three types of power grid regions:
- Balancing authority area (generally smaller regions of the power grid in which all power plants are managed to balance power system demand and supply);
- eGRID subregion; and
- NERC region, as designated by the North American Electric Reliability Corporation (plus Alaska, Hawaii, and Puerto Rico).
Download all the current data here and the historical data here. The eGRID historical ZIP file currently contains data and supplementary files (e.g., technical support documents, maps, summary tables, and release notes) for years 1996, 1997, 1998, 1999, 2000, 2004, 2005, 2007, 2009, 2010, 2012, 2014, and 2016. Net imports-exports by state are provided for years 2004, 2005, and 2007. Data on net imports-exports by state and power interchange between grid regions are included in eGRID data for years 1996 through 2000. Data years after 2016 are not included in the ZIP file but are available for download from the webpage.
4) Who uses eGRID?
eGRID is valuable to those in the Federal Government, state and local governments, non-governmental organizations, companies, and academia. It is also useful to individuals seeking environmental information about the electric power sector in the United States. eGRID is most often used to estimate indirect emissions from electricity purchases, in GHG inventories, for carbon footprinting of electricity purchases, and for estimating avoided emissions from programs and projects that reduce consumption of grid-supplied electricity. eGRID data are cited by many emission inventory and registry protocols, various emission calculation tools and applications, hundreds of academic papers, and consultants; it is used for many research applications and efforts.
Within EPA, eGRID data are used by the following applications and programs: Power Profiler, Center for Corporate Climate Leadership, Portfolio Manager, the Household Greenhouse Gas Emissions Calculator, the Greenhouse Gas Equivalencies Calculator, Green Power Equivalency Calculator, Power Plants and Neighboring Communities, Green Vehicle Comparison: Your Car vs. an Electronic Vehicle, and the Waste Reduction Model (WARM).
When EPA announced the winners of its 2011 “Apps for the Environment” challenge, two winning apps — Light Bulb Finder and Joulebug — used eGRID data.
In 2015, Executive Order 13693 was issued, requiring Federal agencies to reduce their greenhouse gas emissions from direct and indirect activities. The order requires that Federal agencies report their building information in EPA’s Portfolio Manager, which uses eGRID to estimate emission reductions.
Fueleconomy.gov, a partnership between EPA and U.S. Department of Energy (DOE), uses eGRID data to estimate the total GHG emissions from electric and plug-in hybrid vehicles in its Greenhouse Gas Emissions for Electric and Plug-in Hybrid Electric Vehicles calculator.
eGRID is also used by other Federal Government agencies such as Oak Ridge National Laboratory (ORNL) for their Combined Heat and Power and Emissions Savings Calculator, the National Energy Technology Laboratory (NETL) for their sponsored Distributed National Carbon Sequestration Database and Geographic Information System (NATCARB), and the National Renewable Energy Laboratory (NREL) for their micropower distributed generation optimization model named HOMER.
One of the most popular recent uses of eGRID is to determine the indirect GHG emissions from electricity purchases and avoided GHG emissions from projects and programs that reduce the demand for grid supplied electricity. For example, the California Air Resources Board, Climate Registry, Climate Action Reserve, and Greenhouse Gas Protocol cite eGRID for use in estimating scope-2 GHG emissions from electricity purchases in the United States. Most carbon footprint calculators that are applicable to the United States use eGRID data.
State and local governments rely on eGRID data for electricity labeling (environmental disclosure programs), emission inventories, and registries as well as for efforts to analyze air emissions from the electric power sector. Several states have used eGRID to publish state specific emission information or have used eGRID to inform policy decisions.
Renewable energy certificates (RECS) tracking systems, such as ISO-New England’s Generation Information System (GIS) and PJM Interconnection’s Generation Attribute Tracking System (GATS), use eGRID data.
eGRID is used by many nongovernmental organizations in their tools and analysis. One example is Carbon Footprint Visualizations by Carbon Visuals, which illustrates accurate volumetric images to visualize the carbon footprint of all U.S. power stations. Another example is The University of California, Berkeley’s CoolClimate Carbon Footprint Maps.
5) What years are available for eGRID?
The latest version of eGRID (eGRID2022) was the seventeenth edition released in January of 2024 with data from 2022. Links to all the data are available on the Download Data page.
Previous Name | Current Name | Data Year(s) | Edition Number | Release Date(s) |
---|---|---|---|---|
eGRID96 | eGRID1996 | 1996 | First | 12/1/1998 |
eGRID97 | eGRID1997 | 1996-1997 | Second | 12/1/1998 |
eGRID2000 | eGRID1998 | 1996-1998 | Third | 3/1/2001 9/1/2001 |
eGRID2002 | eGRID1999 eGRID2000 |
1996-2000 | Fourth | v1 - 12/2002 v2 - 4/2003 v2.01 - 5/2003 |
eGRID2006 | eGRID2004 | 2004 | Fifth | v1 - 12/21/2006 v2 - 4/2007 v2.1 - 5/2007 |
eGRID2007 | eGRID2005 | 2005 | Sixth | v1 - 10/16/2008 v1.1 - 1/2009 |
eGRID2010 | eGRID2007 | 2007 | Seventh | 2/23/2011 |
eGRID2012 | eGRID2009 | 2009 | Eight | 5/10/2012 |
eGRID2014 | eGRID2010 | 2010 | Ninth | 2/24/2014 |
eGRID2012 | 2012 | Tenth | 10/8/2015 | |
eGRID2014 | 2014 | Eleventh | v1 - 1/13/2017 v2 -2/27/2017 |
|
eGRID2016 | 2016 | Twelfth | 2/15/2018 | |
eGRID2018 | 2018 | Thirteenth | 1/28/2020 v2 - 3/9/2020 |
|
eGRID2019 | 2019 | Fourteenth | 2/23/2021 | |
eGRID2020 | 2020 | Fifteenth | 1/27/2022 | |
eGRID2021 | 2021 | Sixteenth | 1/30/2023 | |
eGRID2022 | 2022 | Seventeenth | 1/30/2024 |
6) What has changed in recent years?
In recent years, there have been several changes to the eGRID content, methodology, and presentation of data. The significant changes starting with the release of eGRID2012 include:
eGRID2012
- Included entire universe of plants and associated generators, including plants with zero generation, which had been excluded from previous editions of eGRID.
- The national-fuel and state-fuel content average, calculated from EIA-923 Schedule 3A, was updated.
- Color coded cross-hatching was added to the subregion map in order to illustrate areas where there are secondary and tertiary service subregions.
- Subregion shapefiles were provided.
- The naming convention changed to include the data year in the title (e.g. “eGRID2012” includes data for 2012); previous naming conventions listed the year eGRID was released rather than the year of the data used.
eGRID2014
- Replaced “Boiler” file with new “Unit” file; included the entire universe of units; not just the subset of boilers with unit-level data from EPA/CAMD or EIA.
- Revised the plant-to-eGRID subregion assignment methodology to be based on where the plant is located rather than where it supplies its electricity (revised again in eGRID2016).
- Revised the grid gross loss (GGL) methodology to use only data from the EIA State Electricity Profiles, rather than a mix of data from EIA and the Federal Energy Regulatory Commission (FERC).
- Modified the combined heat and power (CHP) adjustment methodology.
- Updated the methodology to determine generation and NOX emissions in the ozone season.
- Added unadjusted heat input for renewable fuels (which is calculated by EIA) to the Plant file.
- Added non-baseload generation by fuel type and non-baseload resource mix to the subregion file.
- Added CH4 and N2O emission rates by fuel type to the eGRID Subregion file.
- Moved supplemental data such as historical sequence IDs to another spreadsheet.
- Renamed "Power Control Area" file to "Balancing Authority" file to reflect the terminology currently used by the EIA and NERC.
- Provided a metric unit version of the data file.
- EIA data were allocated to unit level allowing the unit level data sum to equal the plant-level data.
- Added a hyperlinked table of contents and color coding to the data file.
- Identified data sources at a more granular level.
- CH4 emissions factors for coal changed.
- Revised the CHP adjustment calculations to no longer estimate a CHP adjustment ratio for plants where EIA reports the heat input for electricity generation as equal to the total heat input for the plant.
eGRID2016
- Revised the plant-to-eGRID subregion assignment methodology to be based on where the plant supplies its electricity, rather than where the plant is physically located. This change returns the methodology to the approach used in eGRID2012 and previous editions.
- Reported CH4 and N2O output and input emission rates in lb/MWh and lb/MMBtu, rather than lb/GWh and lb/BBtu.
eGRID2018
- Mercury emissions (when available) were included at the unit-level.
- Global warming potential (GWP) values were updated to the Fourth IPCC Assessment values.
- Heat input and emissions values used to adjust CHP plants and biomass plants were added to the plant-level.
- Plant-level sector information was added.
- The number of boilers at the plant-level was changed to number of units.
- The "Plant operator name" field was changed to "Plant transmission or distribution system owner name" and the "Utility service territory name" field was changed to "Utility name."
- CH4 and N2O emission factors for refined coal (RC) and waste coal (WC) were updated (see differences between v1 and v2 here).
- The emission factor for NOX emissions from flaring of landfill gas (LFG) used in the biomass adjustment of LFG was updated.
- Fuel specific nonbaseload generation was added to the State, BA, NERC region, and U.S. levels.
- Input emission rates (lb/MMBtu) for CH4, N2O, and CO2e were added to the Plant, State, BA, eGRID subregion, NERC region, and U.S. levels (revised in v2).
- Fuel specific output emission rates (lb/MWh) for CH4, N2O, and CO2e were added to the State, BA, eGRID subregion, NERC region, and U.S. levels (revised in v2).
- Exports were excluded from the GGL methodology.
eGRID2019
- Data from Puerto Rico were added to the Generator, Unit, Plant, State, Balancing Authority, eGRID Subregion, NERC region, and U.S. files. The addition of Puerto Rico resulted in the addition of a new State (Puerto Rico; PR), Balancing Authority (Puerto Rico Miscellaneous; NA), eGRID subregion (Puerto Rico Miscellaneous; PRMS), and NERC region (Puerto Rico; PR) to the eGRID2019 files.
- Added a new CO2 equivalent combustion output emission rate (lb/MWh) in the Plant, State, Balancing Authority, eGRID Subregion, NERC region, and U.S. files.
- The supporting documentation name was changed from "Technical Support Document "(TSD) to "Technical Guide".
eGRID2020
- The NERC regions ASCC in Alaska and HICC in Hawaii are no longer included in the EIA-860 Plant file and therefore not included in eGRID2020. All plants in Alaska and Hawaii have been assigned to a NERC region matching their state abbreviation (i.e., AK and HI).
eGRID2021
- A flag identifying plants that contain CAMD-level data was added to the plant-level spreadsheet.
- All units that have a "proposed" status and/or units that retired prior to data year 2021 were no longer included in the eGRID data.
- Demographic information from EPA's Environmental Justice Screening and Mapping Tool (EJScreen) was added for each plant in the "DEMO" tab of the spreadsheet.
- The NOX emissions factor for flaring of landfill gas was updated.
- A new data source was used to identify the geothermal plant type.
More information about each of these changes can be found in the “What’s New” sections of the Technical Guide (formerly called Technical Support Document) available with each eGRID release.
7) What is new in eGRID2022?
eGRID2022 is updated with 2022 data and the most recent EJScreen demographic data, which includes the following changes:
- For the socioeconomic and demographic data (DEMO tab):
- All demographic indicators are updated to the Census Bureau’s ACS 2017-2021 5-year Summary (ACS 2021),
- Unemployment rate, Limited Life Expectancy, and Supplemental Demographic Index data were added, and
- Columns were reordered.
Please see the Technical Guide for more details. Because there are some methodological changes in different editions of eGRID from year to year, please use caution when comparing data from different years.
8) How do eGRID2022 subregion rates compare to eGRID2021?
In general, the CO2 output emission rates for most eGRID subregions decreased in 2022 compared to 2021. There are several cases where the emissions rates increased. CO2 output emission rates may fluctuate on an annual basis due to a change in the resource mix (the percentage of generation from each fuel type).
For example, if a subregion decreased dependency on a fossil fuel (e.g., coal, oil, or gas) and replaced it with a renewable source (e.g., nuclear, hydro, biomass, wind, solar, or geothermal), overall CO2 emission rates would likely decrease. Alternatively, if a subregion increased the relative proportion of fossil generation, for example, to replace generation from a retired nuclear plant, the emissions rates may increase.
The changes in the resource mix are often attributed to changes in the number of plants in an eGRID subregion (retirements or additions) or changes to operations at individual plants.
The following maps and graphs show the eGRID subregion 2021 and 2022 CO2 emission rates and percent differences. Clicking an individual subregion brings up a window that displays the data along with information about the resource mix changes for that eGRID subregion.
The maps and charts are available here.
9) Are EIA-923 data updates reflected in eGRID?
Typically, EIA will make corrections to previously issued EIA-923 data. If the corrections are deemed to affect the eGRID data significantly, EPA will release another version of eGRID incorporating the latest EIA updates.
10) What eGRID data year should be used?
For ongoing work, the best practice is to apply the most recent factors available at the time.
When an organization is completing multiple historical years at once, aligning the data year with the reporting period is recommended. For example, 2021 inventory year should use eGRID2021 and the 2022 inventory should use eGRID2022.
If a corresponding eGRID data year is not available, it is recommended to use the eGRID version preceding the inventory year. For example, the 2017 inventory should use eGRID2016.
For carbon footprinting of electricity purchases and GHG accounting, EPA recommends using the output emissions rates from the eGRID subregion level. eGRID subregions replicate the physical constraints of the electricity grid and minimize the effect of electricity transfer between subregions. eGRID subregions are comprised of the larger NERC regions (which can be very big) and balancing authorities (which can be very small). Using the eGRID subregion emission rates for carbon footprinting of electricity purchases purposes will more accurately represent the regional emissions associated with the power consumed at a given location.
eGRID also includes emissions, generation, and emission rates for other geographic levels, including states, NERC regions, balancing authorities, and at the national level. Data for these levels are included in eGRID as a reference, for example, to allow for state-level comparisons of generation or emissions. However, for carbon footprinting of electricity purchases purposes, EPA recommends using the output emissions rates at the eGRID subregion level.
11) Which geographic level of eGRID data should be used to determine emissions from electricity use?
For carbon footprinting of electricity purchases and GHG accounting, EPA recommends using the output emissions rates from the eGRID subregion level. eGRID subregions replicate the physical constraints of the electricity grid and minimize the effect of electricity transfer between subregions. eGRID subregions are comprised of the larger NERC regions (which can be very big) and balancing authorities (which can be very small). Using the eGRID subregion emission rates for carbon footprinting of electricity purchases purposes will more accurately represent the regional emissions associated with the power consumed at a given location.
eGRID also includes emissions, generation, and emission rates for other geographic levels, including states, NERC regions, balancing authorities, and at the national level. Data for these levels are included in eGRID as a reference, for example, to allow for state-level comparisons of generation or emissions. However, for carbon footprinting of electricity purchases purposes, EPA recommends using the output emissions rates at the eGRID subregion level.
12) What are nonbaseload output emission rates and when should they be used?
In addition to annual output emission rates, eGRID provides baseload and nonbaseload output emission rates. The nonbaseload output emission rates include data from power plants that can increase or decrease their production according to daily and seasonal cycles of electricity demand (“load following plants”) or by power plants that only operate when electricity demand is the highest in a region (“peaking plants” or “peakers”). The emission rates from these plants are sometimes called “marginal emission rates” because these rates are representative for plants “on the margin" of operation, that is, plants that will be among the first to change their generation or operation when regional electricity demand changes.
Based on each plant’s operation data, a certain percentage of the emissions and generation ranging from 0% to 100% from each plant is categorized as nonbaseload. The rate, expressed in lb/MWh, is calculated by dividing the total emissions by the total generation at the state, balancing authority, eGRID subregion, NERC region, and U.S. levels.
For plants that produce 20% or less electricity than they are capable of producing, all the plant-level emissions and generation are categorized as nonbaseload (100%). For plants that produce 80% or more electricity than they are capable of producing, all of the plant-level emissions and generation are categorized as baseload (i.e., none of the data are included in nonbaseload emission rates). For plants that produce between 20% and 80% of electricity they are capable of producing, a percentage ranging from 1% to 99% of the emissions and generation are categorized as nonbaseload. Generation from renewable fuels is not included in nonbaseload calculations (such as solar, wind, etc.), but municipal solid waste is included.
Nonbaseload output emission rates can be used to estimate the emissions that could be avoided through projects that displace marginal fossil fuel generation, such as energy efficiency efforts and/or renewable energy.
EPA’s Avoided Emissions and generation Tool (AVERT) can also be used to estimate the emissions from power plants on the margin from various user-defined scenarios. Interested parties can use AVERT to evaluate county, state, and regional changes in energy and emissions from electric power plants and displaced fuel-burning vehicles resulting from energy policies and programs such as energy efficiency, renewable energy, electric vehicles, and energy storage.
Nonbaseload output emission rates should not be used to assign an emission value for electricity use in carbon-foot printing exercises or GHG emissions inventory efforts. Rather, eGRID subregion-level total output emission rates are recommended for estimating emissions associated with electricity use (scope 2 emissions).
More information about nonbaseload rates can be found in section 3.1.3.2 of the eGRID Technical Guide.
13) What is Grid Gross Loss?
More commonly known as line losses, power losses, or transmission and distribution (T&D) losses, the grid gross loss (GGL) is an estimate of the energy lost in the process of supplying electricity to consumers. These losses mainly occur from energy dissipated in the conductors, transformers, and other equipment used for transmission, transformation, and distribution of power. eGRID provides an estimate expressed as a percent of generation for the United States, each NERC interconnection (i.e., Eastern, Western, and ERCOT), Alaska, and Hawaii. EPA estimates that the GGL is about 5% of the electricity that is transmitted and distributed annually in the United States. This estimate is determined in accordance with the methodology used by the U.S. Energy Information Administration (EIA) as described in this FAQ.
The 2022 GGL estimates are:
Power Grid | 2022 GGL (%) |
---|---|
Eastern | 5.1 |
ERCOT | 5.1 |
Western | 5.1 |
Alaska | 5.0 |
Hawaii | 5.4 |
U.S. | 5.1 |
How is GGL calculated?
GGL is calculated by dividing the estimated losses by the result of total disposition minus net interstate exports minus direct use:
The U.S. Energy Information Administration (EIA) provides data on estimated losses (reported at the utility level via form EIA-861, and then allocated to States based on the utility's retail sales by State), total disposition (i.e., the sum of station use, direct use, retail sales, sales for resale, and other outgoing electricity), net interstate exports, and direct use (i.e., electricity consumed onsite for all operations other than electric power plant station use) at the state level in the State Electricity Profiles. EPA aggregates the data and presents it for Alaska, Hawaii, and the Eastern, Western, and ERCOT NERC interconnections. A map of the interconnections is available here.
Has the GGL methodology changed?
To align more closely with estimates made by EIA, starting with the release of eGRID2018, the methodology for calculating GGL changed slightly from the previous methodology used to create GGL values for eGRID2014 and eGRID2016. The previous methodology did not account for interstate trade values that were included in total disposition for each state, which ultimately led to a slight double counting of values. The revised methodology excludes net exports from each state’s total disposition. The formula for calculating GGL remains nearly the same as the previous methodology, with the exception that net interstate exports are subtracted from the total disposition in the denominator.
Estimates of GGL from eGRID2012 and earlier used a different formula based on data on generation, imports, and exports from FERC and consumption data from EIA. eGRID2014 and subsequent eGRID editions use only EIA data, as well as a new formula (as described above). The use of one data source minimizes error due to differences in the way EIA and FERC collect data.
Please see the Technical Guide for more details on the data definitions and methodology.
How do the historical GGL values compare?
The 2012, 2014, 2016, 2017, 2018, 2019, 2020, 2021, and 2022 GGL values are shown in the following graph:
14) How has the methodology for assigning plants to eGRID subregions changed?
While the 26 subregions have not changed substantially since conception, the methodology for assigning plants to subregions has been revised, most notably in eGRID2014 and eGRID2016. The subregion emission rates most accurately represent the actual electricity used by consumers by limiting the import and export of electricity within an aggregated area. The subregions were defined by EPA as a compromise between NERC regions (which EPA felt were too big) and balancing authorities (which EPA felt were generally too small).
In eGRID2012 and previous editions, plants were assigned to eGRID subregions based on a variety of factors, including associated NERC region, Power Control Area (PCA), and transmission/distribution/utility service territory. The methodology was revised in eGRID2014 because information about some of these linkages was no longer available and to make the process for assigning plants to subregions more straightforward, reproducible, and transparent. In eGRID2014, plants were assigned to eGRID subregions by first using the NERC region and then, for the remaining plants, using GIS shapefiles based on a plant’s physical location.
To better meet the intent of the subregions while ensuring that new plants could be assigned consistently and changes in the electrical grid could be captured in subsequent eGRID updates, the methodology for assigning plants to eGRID subregions was revised again. Since eGRID2016, plants have been assigned to subregions using data from EIA and NERC in a five-step process. Assignments are based on each plant’s NERC region, Balancing Authority, and transmission/distribution/utility service territory. For a small number of plants, we also use the plant’s NERC Assessment Area. More information about the plant assignment methodology can be found in section 3.4.2 of the Technical Guide.
15) How has the methodology for estimating methane (CH4) emissions changed?
The CH4 emissions factors which eGRID uses changed in eGRID2014. Subsequent editions continue to use the same factors as used in eGRID2014. The method for estimating CH4 emissions from electricity generation involves multiplying the heat input (mmBtu) by a fuel-specific emissions factor. This is the same methodology used in all editions of eGRID. However, the CH4 emissions factor for all types of coal has been updated in eGRID2014 and subsequent eGRID editions to 0.011 kg CH4/mmBtu from the previous value of 0.001 kg CH4/mmBtu.
The source of these emissions factors is Table C-2 of EPA’s Mandatory Rule on the Reporting of Greenhouse Gases (40 CFR Part 98). Table C-2 includes an emissions factor of 0.011 kg CH4/mmBtu for coal combustion, and in the footnote, the table includes the option of using a lower emission factor of 0.001 kg CH4/mmBtu for coal.
While EPA’s Greenhouse Gas Reporting Program allows the use of either emissions factor when reporting emissions, the majority of users choose to use the higher emissions factor.
To maintain consistency with other GHG reporting methodologies, eGRID revised the emissions factor starting with eGRID2014. The table below presents the revised CH4 emissions rates (lbs. CH4/GWh) for eGRID2010 and eGRID2012 at the subregion-level and also presents the eGRID2014 CH4 output emission rates for comparison. Year-to-year differences in the regional CH4 emission rates are explained by changes in each region’s resource mix.
eGRID Subregion Name | eGRID Subregion Code | CH4 Emission Rate (lb/GWh) | ||
---|---|---|---|---|
eGRID2010* (revised) | eGRID2012* (revised) | eGRID2014 | ||
ASCC Alaska Grid | AKGD | 72.90 | 78.31 | 46.63 |
ASCC Miscellaneous | AKMS | 20.79 | 20.11 | 36.07 |
WECC Southwest | AZNM | 109.09 | 103.76 | 66.38 |
WECC California | CAMX | 53.04 | 51.82 | 33.11 |
ERCOT All | ERCT | 100.06 | 90.99 | 81.84 |
FRCC All | FRCC | 112.16 | 102.78 | 87.78 |
HICC Miscellaneous | HIMS | 203.43 | 171.44 | 95.34 |
HICC Oahu | HIOA | 150.88 | 157.18 | 159.41 |
MRO East | MROE | 225.51 | 214.39 | 191.16 |
MRO West | MROW | 193.35 | 181.64 | 161.37 |
NPCC New England | NEWE | 114.05 | 99.08 | 96.00 |
WECC Northwest | NWPP | 99.89 | 79.43 | 97.81 |
NPCC NYC/Westchester | NYCW | 26.41 | 24.13 | 24.37 |
NPCC Long Island | NYLI | 121.97 | 121.57 | 132.41 |
NPCC Upstate NY | NYUP | 63.45 | 40.55 | 30.69 |
RFC East | RFCE | 101.73 | 79.07 | 73.93 |
RFC Michigan | RFCM | 195.88 | 177.82 | 170.09 |
RFC West | RFCW | 180.11 | 156.50 | 150.20 |
WECC Rockies | RMPA | 195.62 | 176.01 | 178.16 |
SPP North | SPNO | 193.98 | 183.81 | 173.79 |
SPP South | SPSO | 159.52 | 152.22 | 135.44 |
SERC Mississippi Valley | SRMV | 91.70 | 85.67 | 78.63 |
SERC Midwest | SRMW | 212.76 | 200.16 | 208.84 |
SERC South | SRSO | 166.56 | 130.27 | 103.71 |
SERC Tennessee Valley | SRTV | 163.37 | 151.75 | 138.64 |
SERC Virginia/Carolina | SRVC | 140.92 | 120.23 | 95.72 |
* The 2010 and 2012 CH4 emission rates are recalculated using 0.011 kg CH4/mmBtu emissions factors for coal combustion. The CH4 emission rates in the eGRID2010 and eGRID2012 files have not been changed; those rates are based on the 0.001 kg CH4/mmBtu emission factors for coal combustion.
16) What are GWPs and which GWPs does eGRID use?
The global warming potential (GWP) allows comparisons of the global warming impacts of different gases in the atmosphere. Specifically, it is a measure of how much energy the emissions of 1 ton of a gas will absorb over a given period of time, relative to the emissions of 1 ton of carbon dioxide (CO2).
Traditionally, 100-year GWPs are used when calculating overall CO2 equivalent (CO2e) emissions, which is the sum of the products of each GHG emission value and their GWP. Based on the fourth IPCC assessment report (2007) (AR4), the GWP of CO2 is 1, CH4 is 25 and N2O is 298. When calculating the CO2e it is important to use consistent measurement units. EPA presents both imperial and metric eGRID data. For imperial units, CO2 and CO2e emissions are expressed in short tons, while CH4 and N2O emissions are expressed in pounds. For metric units, CO2 and CO2e emissions are expressed in metric tons, while CH4 and N2O emissions are expressed in kilograms.
The GWPs were updated to AR4 in eGRID2018 to align with other EPA sources reporting CO2e emissions, and AR4 is used through eGRID2022. Previous versions of eGRID used the second IPCC assessment (SAR). Future versions of eGRID may use a different GWP to better align with other EPA tools and datasets. A comparison of the GWPs for CO2, CH4, and N2O across SAR (Second IPCC assessment report), TAR (Third IPCC assessment report), AR4 (Fourth IPCC assessment report), and AR5 (Fifth IPCC assessment report) is shown below:
Gas | SAR | TAR | AR4 | AR5 (with climate-carbon feedbacks) | AR5 (without climate- carbon feedbacks) |
---|---|---|---|---|---|
CO2 | 1 | 1 | 1 | 1 | 1 |
CH4 | 21 | 23 | 25 | 34 | 28 |
N2O | 310 | 296 | 298 | 298 | 265 |
The table below shows the eGRID subregion annual CO2e emissions using GWP values from AR4 and AR5 with and without climate-carbon feedbacks. Climate-carbon feedbacks represent the impact that changes in climate can have on the carbon cycle, which in turn can have an additional impact on the climate. More information about climate-carbon feedbacks can be found in chapter 7 of the IPCC Sixth Assessment Report and more information about GWPs can be found here.
CO2e Output Emission Rates (lb/MWh) and Non-Baseload Output Emissions Rates (lb/MWh) by eGRID Subregion
eGRID Region |
AR4 |
AR5 (with climate- carbon feedbacks) |
AR5 (without climate-carbon feedbacks) |
|||
---|---|---|---|---|---|---|
CO2e Output Emission Rate (lb/MWh) |
CO2e Non-Baseload Output Emission Rate (lb/MWh) |
CO2e Output Emission Rate (lb/MWh) |
CO2e Non- Baseload Output Emission Rate (lb/MWh) |
CO2e Output Emission Rate (lb/MWh) |
CO2e Non-Baseload Output Emission Rate (lb/MWh) |
|
AKGD | 1,057.8 | 1,232.5 | 1,058.6 | 1,233.6 | 1,057.7 | 1,232.3 |
AKMS | 497.6 | 1,593.3 | 497.8 | 1,593.9 | 497.5 | 1,593.1 |
AZNM | 779.4 | 1,209.5 | 779.8 | 1,210.1 | 779.3 | 1,209.4 |
CAMX | 499.3 | 1,058.0 | 499.5 | 1,058.5 | 499.2 | 1,058.0 |
ERCT | 774.3 | 1,199.2 | 774.7 | 1,199.9 | 774.2 | 1,199.2 |
FRCC | 816.9 | 1,048.0 | 817.3 | 1,048.6 | 816.8 | 1,048.0 |
HIMS | 1,163.1 | 1,629.6 | 1,164.0 | 1,631.9 | 1,162.8 | 1,630.2 |
HIOA | 1,586.9 | 1,822.9 | 1,588.4 | 1,824.5 | 1,586.6 | 1,822.5 |
MROE | 1,488.7 | 1,682.8 | 1,489.9 | 1,684.2 | 1,488.5 | 1,682.6 |
MROW | 943.4 | 1,807.0 | 944.3 | 1,808.7 | 943.2 | 1,806.7 |
NEWE | 540.5 | 928.1 | 541.1 | 928.7 | 540.4 | 928.0 |
NWPP | 605.9 | 1,524.7 | 606.4 | 1,525.9 | 605.8 | 1,524.5 |
NYCW | 886.6 | 973.0 | 886.8 | 973.2 | 886.6 | 973.0 |
NYLI | 1,209.3 | 1,319.1 | 1,210.5 | 1,319.4 | 1,209.1 | 1,319.0 |
NYUP | 275.4 | 922.5 | 275.5 | 923.1 | 275.4 | 922.7 |
PRMS | 1,599.9 | 1,676.7 | 1,600.7 | 1,677.4 | 1,599.7 | 1,676.5 |
RFCE | 660.3 | 1,285.1 | 660.7 | 1,286.0 | 660.2 | 1,285.0 |
RFCM | 1,224.2 | 1,607.4 | 1,225.2 | 1,608.7 | 1,224.0 | 1,607.1 |
RFCW | 1,005.9 | 1,855.7 | 1,006.7 | 1,857.3 | 1,005.8 | 1,855.4 |
RMPA | 1,131.7 | 1,685.1 | 1,132.6 | 1,686.2 | 1,131.6 | 1,684.8 |
SPNO | 959.4 | 1,956.5 | 960.3 | 1,958.3 | 959.2 | 1,956.1 |
SPSO | 975.3 | 1,535.2 | 975.9 | 1,536.2 | 975.1 | 1,535.1 |
SRMV | 803.7 | 1,225.6 | 1,262.0 | 1,226.3 | 803.6 | 1,225.5 |
SRMW | 1,380.2 | 1,821.2 | 1,700.3 | 1,822.9 | 1,379.9 | 1,820.9 |
SRSO | 897.7 | 1,361.1 | 788.3 | 1,361.9 | 897.5 | 1,360.9 |
SRTV | 938.6 | 1,681.3 | 684.8 | 1,682.7 | 938.5 | 1,681.1 |
SRVC | 625.9 | 1,315.1 | 506.7 | 1,316.3 | 625.8 | 1,315.3 |
Total | 827.5 | 1,412.5 | 828.1 | 1,412.3 | 827.4 | 1,413.5 |
17) Did the eGRID naming convention change?
Yes, the naming convention changed starting with the release of eGRID2012 (October 8, 2015). The year noted in the title reflects the data year rather than the release year. For example, the eGRID file released in 2012 with 2009 data was previously named eGRID2012; using the new naming convention, it’s now called eGRID2009.
eGRID2012 and subsequent editions (and associated materials) reference previous eGRID editions using the new naming convention, and the files available for download from the website use the new naming convention. However, the content within the previous editions of eGRID, such as the technical support documents, has not been revised.
18) Is there additional eGRID data available?
Yes, additional data files are available. Beginning with eGRID2014, the data are also presented in International System of Units (SI) and are available in the metric data file. The Historical Sequence ID Fields (XLSX) (xlsx) that were reported in the Plant file in past editions of eGRID are included as a separate file (discontinued with the release of eGRID2019). The code descriptions are available on the code lookup webpage, in the Technical Guide, and in the eGRID Code Lookup (xlsx) file. Images, shapefiles, and geodatabases are available here. An excel version, Power Profiler Emissions Tool (xlsx) of Power Profiler is also available.
19) What do the eGRID subregion and NERC region maps look like?
The maps are representational. Many of the boundaries shown on the maps are approximate because they are based on companies, not on strict geographical boundaries. On the Maps webpage, images are available for the eGRID Subregion Map and the NERC Region Map. An eGRID shapefile and geodatabase are also available.
20) How has the subregion map changed?
The subregion map was noticeably revised with the release eGRID2012; however, no significant changes to the map have been made since then. Beginning with eGRID2012, cross-hatching on the map identifies areas where more than one eGRID subregion may apply. While the majority of zip codes are located within only one eGRID subregion, in some cases a zip code may fall in multiple eGRID subregions because it is supplied by different service providers associated with different subregions. This usually occurs near the borders of two subregions. In eGRID2012, the map identified “secondary” and “tertiary” subregions; however, starting with eGRID2014, the map simply indicates areas that fall into more than one eGRID subregion without identifying “secondary” and “tertiary” subregions.
If you live in an area with multiple electric service providers (illustrated by cross-hatching on the map), the map isn’t sufficient to tell you the eGRID subregion associated with your location. For this information, you must enter your zip code and electric service provider information into Power Profiler to definitively determine your appropriate eGRID subregion.
The boundaries shown on this map are not based on strict geographical boundaries. In some cases, plants assigned to a particular eGRID subregion may be located far away from most of the other plants in that subregion. For example, the Intermountain Power Project plant is assigned to the CAMX subregion, yet this plant is located in Utah. This plant was assigned the CAMX subregion based on its balancing authority, which is the Los Angeles Department of Water and Power. GIS shapefiles for the eGRID subregions and NERC regions are available here.
21) What are the regional emission rates and resource mix?
The most recent state and eGRID subregion information can be found in summary tables available as either an Excel or PDF format. The summary tables for previous years can be found with the historical data.
22) How can I receive eGRID related news from EPA?
If you are interested in receiving email alerts when eGRID is updated or eGRID related news is released, sign up at eGRID Notification form.
23) What other emissions data are available from EPA?
Most of the eGRID emission data are from the Clean Air Power Sector Programs of EPA. In addition to the hourly emission data reported to EPA from power plants affected by the Acid Rain Program and/or the Cross-State Air Pollution Rule, the Clean Air and Power Division website presents progress reports, power plant emission trends, and emissions tracking highlights. Other EPA emission data sources also provide data on emissions associated with electricity generation. Air Trends Reports are EPA's "report card" on the status of air quality and air pollutant emissions. Reports are published annually, about ten months after year-end. U.S. Greenhouse Gas Inventory Reports include inventories of U.S. greenhouse gas emissions and sinks. The Greenhouse Gas Reporting Program (GHGRP) requires reporting of greenhouse gas (GHG) data and other relevant information from large GHG emission sources, fuel and industrial gas suppliers, and CO2 injection sites in the United States. Also, see the National Emissions Inventories for the U.S. and the Toxics Release Inventory.
24) Why are there outliers for some output emission rates?
The output emission rates (e.g. lbs. CO2/MWh) in some eGRID subregions are significantly higher than the rates in other regions. This is particularly true for the emission rates by fuel type, such as the emission rates for oil. For example, the CO2 output emission rate for oil in the RMPA subregion is significantly higher than the oil rates for most other regions. This is due to plants with negative net electricity generation. The generation data in eGRID are from the Energy Information Administration (EIA), which defines net generation as the total gross generation minus station use (which is the amount of electricity used to operate and maintain the electric power plant). In some cases, the amount of station use electricity exceeds the total amount of electricity generated at the plant, and the total net generation is a negative number. However, these plants still have positive emissions. When the emission rates are calculated at the subregion level, the sum of the emissions from all plants in that subregion are divided by the sum of the generation from all plants in that subregion. If there are several plants that report negative net generation, then it can reduce the denominator of that equation and result in a higher overall output emission rate. For a fuel type such as coal or natural gas, which is the primary fuel type for many plants in each region, negative net generation does not have much impact on the overall emission rate. For a fuel type such as oil, which is the primary fuel type for relatively few plants in each region, negative net generation may have much more of an impact on the emission rates.
25) Why are there differences at a small number of plants between total net generation and generation by fuel type?
eGRID reports both the total net generation (MWh) and net generation from each fuel type at each plant in the Plant file. For a relatively small number of plants (less than 0.1%), the sum of the generation by fuel type does not equal the total net generation at the plant. The reason for this is because eGRID uses two different data sources from the Energy Information Administration (EIA) to determine net generation at each plant. EIA provides net generation at the unit level for a subset of plants in the United States. It also provides net generation at the prime mover level for all plants. The net generation in the Generator file is based on unit-level generation data where available. For generators where unit-level generation data are not available, the generation is based on prime mover-level generation, distributed to each unit based on proportion of nameplate capacity. The total plant-level net generation in the Plant file is the sum of net generation at each plant from the Generator file. The generation by fuel type in the Plant file is based only on the prime mover-level generation data. But there are some cases where there are discrepancies between the unit-level and prime mover-level data from EIA. As a result, there are a handful of plants where the total plant-level generation does not equal the sum of the generation by fuel type.
26) What other EPA tools are available to estimate avoided emissions from EE/RE programs?
The AVoided Emissions and geneRation Tool (AVERT) calculates the change in PM2.5, NOX, SO2, CO2, NH3, and VOCs emissions due to energy efficiency (EE), renewable energy (RE), and electric vehicle (EV) policies and programs. Use AVERT’s web edition or Excel-based tool to create custom calculations that reflect variations in hourly impacts of different EE programs or RE resources within one of AVERT’s fourteen regions. For example, users can select among wind, solar, and different EE savings options within the tool.
AVERT produces outputs including maps, charts, and tables that display the location of emission reductions at the regional, state, and county level, on a monthly and annual basis. Custom analysis using the Excel-based tool can be used for short-term Clean Air Act Plan demonstrations, such as NAAQS SIPS, state-wide EE/RE policies, and to assess impacts of user-designed hourly generation or load profiles.
In 2017, EPA published the first set of AVERT-generated regional and national emission factors. Analysts can use these emission factors to compare the emissions impacts of wind, solar, and energy efficiency program impacts.
27) Can I use eGRID data commercially and how do I cite it?
eGRID data is produced by the United States Environmental Protection Agency (EPA) under the public domain and is available for use both non-commercially and commercially. The following citations for eGRID Data are suggested:
APA: United States Environmental Protection Agency (EPA). (2024). Emissions & Generation Resource Integrated Database (eGRID), 2022. Washington DC: Office of Atmospheric Protection, Clean Air Markets Division. https://www.epa.gov/egrid.
MLA: United States Environmental Protection Agency (EPA). “Emissions & Generation Resource Integrated Database (eGRID), 2022.” Office of Atmospheric Protection, Clean Air Markets Division, 2024, Washington DC. https://www.epa.gov/egrid.
Chicago: United States Environmental Protection Agency (EPA). Emissions & Generation Resource Integrated Database (eGRID), 2022. Washington DC: Office of Atmospheric Protection, Clean Air and Power Division, 2024. https://www.epa.gov/egrid.
28) How can I provide feedback or ask questions?
Your input and feedback is greatly appreciated. Fill out this short survey to let us know how you use eGRID, what data you currently use, what features you would like in subsequent versions, and suggestions for improvements. Additionally, if you have questions or comments, you can submit them through this web form or email EPA directly.