The Climate Trust has developed marginal grid intensity factors for U.S.-based projects that displace grid electricity to assist in calculating such a project’s carbon dioxide offsets.
U.S. Electricity Grid Intensity Factors
For projects submitted for the U.S. GHG Offsets Acquisition Initiative 2007 RFP, Initiative Participants request project developers use the following grid intensity factors. Use these factors when calculating the carbon dioxide offset potential of a project. These guidelines apply for both projects that supply electricity to the grid (renewable generation, cogeneration, power plant upgrades, etc.) as well as projects that reduce demand for electricity (energy efficiency). For a map of the U.S. electricity grid subregions, click here.
Important Note: Updated eGRID emission rates for the eGRID subregions are expected to be released by the U.S. EPA soon. The Climate Trust will update the U.S. Combined Margin Grid Intensity Factors Chart as soon as the information becomes available. Project proposals accepted into Phase II will be asked to recalculate offset projections using the updated Combined Margin Grid Intensity Factors.
This map is of the NERC (National Energy Reliability Council) subregions. Regions are also referenced by their eGRID subregion name, show in parenthesis in the chart above. This map is courtesy of the US Environmental Protection Agency’s eGRID.
If you are unsure of the subregion for your project, please utilize the EPA’s Power Profiler and follow these directions:
Enter the Power Profiler.
Enter the zip code of your project.
Select the electric utility (it does not matter which one), click “Next.”
Click on the link to “your region of the power grid.”
Find the emissions factor for that region in the chart above.
Methodology for Combined Margin Grid Intensity Factors for U.S. Projects
The marginal grid intensity factors are derived from two, evenly weighted factors: 50% marginal grid intensity and 50% marginal build (the power facility displaced by the offset project).
This combined margin factor was selected for the following reasons:
It is an appropriate compromise between the two arguments that offset projects displace the marginal power on the grid and that offset projects displace the marginal build.
A combined margin factor is one of the quantification methodologies approved by the Clean Development Mechanism’s Executive Board.
It is one of the methodologies under assessment by the GHG Protocol's Grid Connected Electricity Sector Workgroup.
Marginal grid intensity: The marginal grid intensity factors were calculated using a weighted average of the emission rates of the fossil fuel plants for the specific region. It has been determined that U.S. EPA’s eGRID has the most useful regional data on emission rates. One of the preferred methods to determine marginal power sources is to use data on the power plant rate order (the order in which the power facilities are utilized to meet demand). As eGRID does not contain such data, the weighted average of the fossil emissions rates was used as a proxy.
Marginal build: For the marginal build factor, it is assumed that the most likely next build will be natural gas with an emissions factor of 0.81 pounds/kWh. This assumption was applied to all regions. The U.S. Energy Information Agency's Annual Energy Outlook 2005 provided the best available information on regional projections of power capacity additions. The report states that the majority of new generation from 2005-2015 will be natural gas. Although a combination coal/natural gas emissions factor could be used for several regions, it has been determined that a natural gas factor is a more conservative assumption from an offset quantification standpoint.
