The information in this table can be used to calculate the greenhouse gas (GHG) emissions associated with untracked and unclaimed U.S.-based sources of electricity, based on location of consumption. The table provides the “Green-e® residual mix emissions rate,” an emissions rate that is adjusted to remove all Green-e® Energy certified sales for each Emissions & Generation Resource Integrated Database (eGRID) subregion  (see eGrid subregion map).
Green-e® residual mix emissions rates are published every Spring using Green-e® voluntary renewable energy market sales data collected during the annual Green-e® verification audit from two calendar years prior and the most recent U.S. generation and emissions rate at the time of publication. It does not include any data that is not reported to Green-e. The residual mix emissions rate used should be based on the eGRID subregion in which the electricity is consumed. Individuals can figure out which eGRID subregion in which they are located by using the EPA’s Power Profiler tool: https://www.epa.gov/energy/power-profiler.
Scope 2 Reporting
When calculating the emissions from unspecified purchased or acquired electricity (considered “Scope 2” emissions, as defined by the World Resources Institute [WRI]), where more-accurate information about the resources and emissions associated with electricity use is not available from the user’s state, region, or electricity supplier, residual mix emissions rates should be used. Regional residual mix emissions rates that factor out all specified electricity purchases are not yet available for all regions of the U.S. or published by a national data source. Until such time, Green-e® residual mixes are available, which factor out all Green-e® certified sales of renewable energy. Users reporting their GHG data should cite the use of these residual mix rates in their accounting. Use of these numbers is compatible with WRI’s Greenhouse Gas Protocol Scope 2 Guidance, which defines residual mix in more detail. Green-e® Energy also offers the Green-e® Energy Summary of WRI Scope 2 Guidance, a guide for purchasers of Green-e® Energy certified renewable energy on how to calculate Scope 2 emissions.
Residual Mix Rate Calculation Methodology
These rates were calculated using the data collected by Green-e® Energy during annual verification of 2017 certified sales and the most recent emissions and generation data provided by eGRID in the U.S. for each eGRID subregion.
The residual mix emissions rate is calculated by first subtracting all unique Green-e® Energy certified sales (in megawatt-hours [MWh]) from the total generation within each subregion. The total CO2 emissions for each region are then divided by this new generation number for each subregion, resulting in an adjusted emissions rate (lb CO2/MWh) that accounts for use of renewable energy from a Green-e® Energy certified product.
For this calculation, each U.S.-generated MWh is assigned to a specific eGRID subregion, with generating facilities assigned to eGRID subregions using facility zip codes and Energy Information Agency data. Generation from facilities that cannot be readily assigned to eGRID subregions is excluded from these residual mix emissions rates.
2019 Green-e® Residual Mix Emission Rates (2017 Data)
|eGrid Subregion||CO2 Emissions (tons)||Net Generation (MWh)||Emission Rate (lb / MWh)||Voluntary RE emissions (lbs)||Voluntary RE (MWh)||Adjusted System Mix (lbs / MWh)||Difference (lbs / MWh)||% Difference|
 eGRID subregions are identified and defined by EPA and were developed as a compromise between NERC regions (which EPA felt were too big) and balancing authorities (which EPA felt were generally too small). Using NERC regions and balancing authorities as a guide, the subregions were defined to limit the import and export of electricity in order to establish an aggregated area where the determined emission rates most accurately matched the generation and emissions from the plants within that subregion.
 The Green-e® Energy Summary of WRI Scope 2 Guidance is available at https://www.green-e.org/docs/energy/Scope2Summary.pdf
 U.S. EPA's Emissions & Generation Resource Integrated Database (eGRID). eGRID2016 (released 2/15/2018) contains the complete release of year 2016 data, https://www.epa.gov/energy/emissions-generation-resource-integrated-database-egrid.
 Unique Green-e® Energy certified sales remove any MWh associated with a Green-e® Energy certified retail sale for which the supply was purchased via a Green-e® Energy certified wholesale transaction, since these two sales represent the same MWh of generation.