Quantification
To determine whether there is an appreciable emissions benefit to include in a State or Tribal Implementation Plan (SIP/TIP), the first step is to understand the potential energy savings and emissions impacts of Energy Efficiency and Renewable Energy (EE/RE) policies and programs in your jurisdiction.
Data:
To develop the emissions projections for estimating future baseline emissions of the electric power sector, your state can use credible and accessible energy forecasts to help reflect the energy impacts of existing EE/RE policies. These energy forecasts are produced by federal and state agencies, utilities, Public Utilities Commissions (PUC) and electric transmission independent system operators.
For example, the U.S. Energy Information Administration (EIA) produces an Annual Energy Outlook (AEO) each year that provides long-term projections of energy supply, demand, and prices, based on data it collects from various industry sources. EPA analyzes state EE/RE policies that are adopted in state law and codified in rule or order, but that are not reflected in the EIA's AEO 2010 electricity demand projections.
A tool that estimates the emissions benefits of energy efficiency and renewable energy policies and programs for specific state-level EE/RE policies. States can adjust their forecasts to reflect missing policies, when applicable.
Methods:
Methods to quantify emissions reductions vary in complexity, rigor, resource implications, and data requirements. Refer to Roadmap, Appendix 1 for more information.
Methods range from basic to sophisticated:
- eGRID Non-baseload Emissions Rate Method
- Capacity Factor Emissions Rate Method
- Historical Hourly Emissions Rate Method
- Energy Modeling Method
To choose the method that best meets your needs, consider the following questions:
- What is the purpose of the analysis?
- What staff expertise is available?
- What budget resources are available?
- What energy information is available?
Emissions Quantification Methods Comparison:
This table can help you select the best method for your situation:
| Key Considerations |
Methods |
||||
|---|---|---|---|---|---|
| eGrid non-baseload | Capacity Factor | Hourly Emissions | Energy Modeling | ||
| Purpose | Preliminary Analysis | well-suited for intended purpose |
well-suited for intended purpose |
well-suited for intended purpose |
not well-suited (either too costly or not robust enough) |
| Voluntary Programs | well-suited for intended purpose |
well-suited for intended purpose |
well-suited for intended purpose |
not well-suited (either too costly or not robust enough) |
|
| General Benefits Info | well-suited for intended purpose |
well-suited for intended purpose |
well-suited for intended purpose |
well-suited for intended purpose |
|
| Regulatory or statutory requirement |
not well-suited (either too costly or not robust enough) |
acceptable* | well-suited for intended purpose |
well-suited for intended purpose |
|
| Emissions | Pollutants of interest | CO2, NOx, SO2, CH4, N2O |
NOx, SO2, CO2 | NOx, SO2, CO2 | NOx, SO2, CO2, varies |
| Scale | Geographic | eGRID subregion | eGRID subregion | Regions vary | modeling regions |
| Imports & Exports | Only within eGRID regions |
Only within eGRID regions |
Depends on size of regions |
Fully addressed | |
| Source Aggregation | Boiler, generator, plant |
Power plant or Electric Generating Unit (EGU)** |
Electric Generating Unit (EGU) |
Electric Generating Unit (EGU) |
|
| Temporal - time scale, historical vs forecasted |
Annual & ozone season (NOx) historical |
Annual & ozone season (NOx) historical |
Hourly historical |
Annual, seasonal, hourly forecasted |
|
| Resources | Time | Low | Low | Medium | High |
| Money | Low | Low | Medium | High | |
| Staff Expertise | Low | Low | Medium | High | |
Notes:
* Better suited when electric generating unit (EGU) capacity factors are used and future generation is included. When appropriate, the outputs could also be at the county level. See Roadmap, Appendix I for details.
** Electric generator units encompass boilers, combustion turbines, internal combustion engines, or other electric generating technologies.
Emissions Quantification Tool:
EPA has developed the AVoided Emissions and geneRation Tool (AVERT). AVERT employs the historical hourly emissions rate approach, and uses statistics to project the hourly changes in generation - and the associated changes in air emissions - at individual generating units that are a result of the introduction of new energy efficiency (EE) or renewable energy (RE) resources in a specific geographic region in the contiguous United States.
The purpose of AVERT is to provide NOx, SO2, and CO2 estimates of the changes in large stationary source emissions (25 MW or greater) that result from new EE/RE policies, programs and measures. It allows users to explore multiple energy efficiency and renewable energy scenarios without having to invest in formal, resource intensive production cost models.