Using eGRID Data to Approximate Operational Carbon

 

Defining "The Grid"

Energy efficiency will remain a cornerstone of sustainable design for the foreseeable future for two big reasons: utility costs and operational carbon.

Anecdotally, we know that the electricity delivered to a building site from a local utility comes from a complex network of power plants (generation stations), substations, and transmission lines - collectively termed an electrical grid (also known a utility grid, power grid, or simply "the grid").

The grid requires enormous monetary capital to procure energy resources, generate electricity, distribute the electricity, operate the infrastructure of generation and distribution such that electricity is delivered uninterrupted for over 99.9% of the year, and maintain the infrastructure as wears out and/or becomes damaged. Utility companies require revenue to offset expenses; therefore, costs are passed on to the customer base. Therefore, less electricity consumption means less money required to operate the building. 

Then, there's the operational carbon emissions consideration. The specific combination of energy resources harvested to produce electricity will consequently result in greenhouse gas (GHG) emissions. Moreover, the various GHG emissions across the value chain for the utility enterprise must also be incorporated. As a building uses the electricity to operate, the GHH emissions attributed to the amount of electricity expended can be equated into equivalent carbon dioxide emissions (CO2e). The total CO2e emissions attributed to building operations (electricity as well as natural gas, if applicable) constitute a basic definition of operational carbon ("carbon" used as a shorthand for CO2e).

 

How Can Operational Carbon Be Calculated?

Less one goes down the rabbit hole of very detailed and nuanced methodologies for questionably greater accuracy, a building's operational carbon from purchased (and therefore "consumed") electricity can be determined by a straightforward calculation: 

kilowatt-hours utilized × emission factor 

The emissions factor defines the carbon intensity of the utilized electricity using a approximated total based on the average grid mix for the region in which the property is located.

In practice, one could pull kWh from utility bills and look up the most regionally appropriate emission factor during that time period (typically offered in units of kg CO₂-e /kWh), multiply them together and - voila! - operational carbon emissions.

 

What is eGRID and Why Does it Matter?

The Emissions & Generation Resource Integrated Database (eGRID) is a comprehensive source of data on the environmental characteristics of nearly all electric power generated in the United States. Developed by the U.S. Environmental Protection Agency (EPA), eGRID began in the late-1990s as the EPA’s first national attempt to link the air pollution records coming from power plant smokestacks with the electricity generation data reported by the Energy Information Administration (EIA).

Since its inaugural public release in December 1998, the eGRID database has grown from a one-off compilation covering 1996-1997 to an annually updated, multi-pollutant resource that underpins federal GHG accounting guidance, corporate GHG emissions inventories, the EPA’s Power Profiler, and dozens of policy tools and information resources.

 

What Sort of Information Does eGRID Provide?

eGRID offers publicly available emissions data for the electric power sector based on available information for all U.S. electricity generating stations that provide power to the electric grid and report data to the federal government. Information reported include, but are not limited to:

• Net electric generation
• Resource mix (for renewable and nonrenewable generation)
• Mass emissions of carbon dioxide (CO₂), nitrogen oxides (NOₓ), sulfur dioxide (SO₂), methane (CH₄), and nitrous oxide (N₂O)
• Emission rates for CO₂, NOₓ, SO₂, CH₄, and N₂O;
• Heat input
• Nameplate capacity

It is important to note that eGRID reports information on an annual basis (as well as by ozone season for NOₓ) at different levels of aggregation. Most recently, eGRID2023 was released in January 2025.

 

eGRID Subregions

When it comes to carbon emissions attributed to utility-purchased electricity, location matters. 

Through a methodology by which the EPA groups together generation stations whose power is most often consumed within the same generalized electrical “neighborhood" as defined by certain practical and technical considerations, eGRID establishes various "subregions," which establish a location-based key that underpins the EPA’s emission factors.

The 27 subregions in eGRID2023 are defined in the figure below.

 

The acronym and name (as well as an abbreviated description) for each eGRID Subregion in eGRID2023 is as follows:

AKGD - ASCC Alaska Grid (South/Central Alaska)

AKMS - ASCC Miscellaneous (Most of Alaska)

AZNM - WECC Southwest (Southwest U.S.)

CAMX - WECC California Southwest Coast/Most of California

ERCT - ERCOT All (Most of Texas)

FRCC - FRCC All (Most of Florida)

HIMS - HICC Miscellaneous (Hawaii excluding Oahu)

HIOA - HICC Oahu (Oahu Island)

MROE - MRO East (Eastern Wisconsin)

MROW - MRO West (Upper Midwest)

NEWE - NPCC New England (New England)

NWPP - WECC Northwest (Northwest U.S.)

NYCW - NPCC NYC/Westchester (New York City)

NYLI - NPCC Long Island (Long Island, New York)

NYUP - NPCC Upstate NY Upstate New York

PRMS - Puerto Rico Miscellaneous (Puerto Rico)

RFCE - RFC East (Mid Atlantic)

RFCM - RFC Michigan (Most of Michigan)

RFCW - RFC West (Ohio Valley)

RMPA - WECC Rockies (Colorado-Eastern Wyoming)

SPNO - SPP North (Kansas-Western Missouri)

SPSO - SPP South (Texas Panhandle-Oklahoma)

SRMV - SERC Mississippi Valley (Lower Mississippi Valley)

SRMW - SERC Midwest (Middle Mississippi Valley)

SRSO - SERC South (Southeast US, Gulf Coast)

SRTV - SERC Tennessee Valley (Tennessee Valley)

SRVC - SERC Virginia/Carolina (Virginia/Carolinas)

For more information on eGRID2023, please consult the EPA's Technical Guide for eGRID2023 as well as the resources available through the eGRID website: epa.gov/egrid

 

Determining Emissions Factors

Using eGRID data, the EPA posts summary data including subregion and state-level emission rates, resource mix information, and grid gross loss values.

For instance, a project located in Indianapolis, Indiana may consider the following total output emission rates from eGRID2023:

RFCW: 911.3 lb CO₂/MWh (413.3 kg CO₂/MWh)

Indiana: 1,457.2 lb CO₂/MWh (661.0 kg CO₂/MWh)

There are other publicly available technical resources for determining emission rates, including the National Renewable Energy Laboratory's (NREL's) Cambium datasets. When it comes to applying emissions factors, users should carefully consider the nature of the resources utilized and the methodology employed to develop their data in order to ensure accuracy and validity.