We understand that the change from NERC regions to eGrid regions is challenging from a communications perspective given the change in system bounds and emission factors. Below, please find more information about why we made the change from residual emission factors by NERC region to residual emission factors by eGrid region.
We made the change from residual emission factors by NERC region to residual mix emission factors by eGrid region for two reasons:
1) The residual mix emission factors will only be available by eGrid region in the future
Green-e, the organization that calculations residual mix emission rates, is now calculating the residual mix emission factors by eGrid region. See this page for more information about their 2017 calculations; their 2016 and 2015 results by eGrid region (which are on SIMAP now) will be posted online soon.
Previously, Green-e was only able to calculate the residual mix emission factors by the aggregated NERC regions because of limited data availability. Now, with a more robust data set, they are offering (and will continue to offer) the residual mix emission factors by eGrid region.
2) The eGrid regions are more accurate than the aggregated NERC regions
The residual mix emission factors by eGrid region are also more accurate than the factors by NERC region for your scope 2 footprint. That is because the NERC regions were more aggregated, meaning they often included a much bigger land area and much more of the electricity grid. Below are maps of the two types of regions.
Here are two pages on SIMAP with more information about the new and old scope 2 calculations in SIMAP:
- Scope 2 methods for outdated emission factor versions (2017 and 2018) that used NERC regions
- Scope 2 methods for recommended version of emission factors (2019) that uses eGrid regions
Remember, the most accurate and preferred scope 2 emissions factor is actually a custom supplier specific emissions factor. The supplier-specific emissions factor comes directly from your local utility, so it is the most accurate representation of the energy mix you are purchasing from the grid. It also means that you would not need to use the regional data sets for emission factors (eGrid, residual mix, etc.) because your custom supplier-specific emissions factor would be used in your calculations.
See this page for more information about the supplier-specific emission factors (how to request it, where to enter it in SIMAP, etc.).