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State and Local Climate and Energy Program

Assessing Air Quality, Greenhouse Gas, and Public Health Benefits

What are the Air Quality, Greenhouse Gas, and Public Health Benefits of Clean Energy?

Electricity generation from fossil fuels is a major source of various types of air pollution. Many states and localities are exploring or implementing clean energy policies to achieve reductions in greenhouse gases (GHGs) and criteria air pollutants, such as particulate matter, ground level ozone, carbon monoxide, sulfur oxides, and nitrogen oxides. While GHGs have a global effect, contribute to climate change, and can last more than 100 years, criteria air pollutants have a local to regional effect on air quality and human health and can dissipate in hours or days. Clean energy measures that reduce criteria air pollutants, therefore, can result in almost immediate local improvements in air quality and human health.

Tools and methods are available to help states estimate the impact of clean energy policies on criteria air pollutant emissions, ambient air quality, and the related environmental and health impacts.

Steps in Estimating Benefits

Develop and project a baseline emissions inventory Select method, compile emissions from available sources into inventory, and develop a forecast.
Quantify emission reductions Develop emissions from clean energy using energy savings estimates, load profile, emissions factors, and control technology or fuel data. Compare against baseline.
Estimate changes in air quality resulting from emission reductions Use criteria air pollutant data to estimate changes in air quality with an air quality model.
Estimate human health and related economic effects of air quality changes Use data on air quality changes and epidemiological and population information to estimate health effects. Apply economic values of avoided health efforts to monetize benefits.

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Developing an Emissions Inventory Forecast Baseline

States can use many sources of data as they compile top-down or bottom-up inventories. Some of these data sources focus specifically on criteria air pollutants, some focus on GHGs, and some include both. More information is available about Developing a GHG Inventory.

Sources of Air Pollutant and GHG Emission Data
Date Source Type of Air Pollutant or GHG Emissions Approach
SO2 NOX CO2 Other GHGs Hg Top
National Emissions Inventory (NEI)
Emissions Collection and Monitoring Plan System (ECMPS)
World Resources Institute Climate Analysis Indicators Tool Exit EPA disclaimer
State GHG Inventories
Local GHG Inventories

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State Examples

Evaluation of the Wisconsin Focus on Energy Program's energy efficiency and renewable energy projects funded by the Utility Public Benefits fund shows that from program inception in July 2001 through June 30, 2006, the state displaced annual emissions from power plants and utility customers of about:

  • 5.8 million pounds of NOX
  • 2.6 billion pounds of CO2
  • 11.4 million pounds of SO2
  • 46 pounds of mercury (Hg)

In 2004, the Texas Commission on Environmental Quality evaluated the Texas Emissions Reduction Plan and calculated that it achieves an annual reduction of NOx emissions of 346 tons through energy efficiency and renewable energy. NOx reductions over the period 2007—2012 are projected to range from 824 tons per year in 2007 to 1,416 tons per year in 2012.

Quantifying Emission Reductions

States can use a range of tools and approaches to quantify the emissions changes from clean energy policies, which can then be compared to the baseline emissions inventory to determine emission benefits.

Basic approaches provide policymakers with approximate estimates of emission reductions they can use for preliminary short-term studies and program evaluation or design. They are often less expensive than more complicated models, but because of their simplicity they are unable to provide the levels of detail that some policymakers require.

Sophisticated approaches are more complex and can offer a wider range of modeling options. These tools provide policy makers with richer insight into the range of emission results and are appropriate to use for regulatory decisions and long-term analyses. They are more costly to run, however, and can require significant technical expertise.

The Comparison of Approaches (PDF) (1 p, 34K, About PDF) table gives more information on advantages, disadvantages, uses, and tools for both basic and more sophisticated options.

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Modeling Air Quality Changes

Clean energy policies that reduce both primary (e.g., NOX) and secondary (e.g., ozone) air pollutants may improve ambient air quality. States can use models to estimate changes in ambient air quality, such as those currently used for State Implementation Plans, as required by the Clean Air Act.

Modeling ambient air quality impacts can be a complex task requiring sophisticated air quality models and extensive data inputs (e.g., meteorology). States can use one of three types of models to conduct this type of analysis: dispersion models, photochemical models, and receptor models. All of the models require location-specific information on emissions and source characteristics, although they may represent photochemistry, geographic resolution, and other factors to very different degrees. States can learn more information about these models through EPA's Support Center for Regulatory Atmospheric Modeling (SCRAM).

Estimating Health Effects and Related Economic Value

Where clean energy measures improve air quality or avoid damage to air quality, they may prevent negative health incidences, such as illnesses and deaths. States can use basic and sophisticated modeling approaches to estimate the human health effects of air quality changes and the monetary value of avoided health effects-a key component of a comprehensive economic benefit-cost analysis. This information can help states compare across alternative program options and communicate some of the most important advantages of clean energy.

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Tools & Resources

Assessing the Multiple Benefits of Clean Energy

Assessing the Multiple Benefits of Clean Energy: A Resource for States provides an overview of the multiple benefits of clean energy and their importance. It includes information on:

  • The importance of and approaches to calculating or estimating energy savings as the foundation for deriving multiple benefits
  • A range of tools and approaches to estimating energy systems, environmental, and economic benefits across varying levels of rigor
  • How states have supported the use of clean energy through the estimation of multiple benefits

Clean Air and Climate Protection Software Tool (CACPS)

CACPS Exit EPA disclaimer calculates and tracks emissions and reductions of greenhouse gases (carbon dioxide, methane, nitrous oxide) and criteria air pollutants (NOX, SOX, carbon monoxide, volatile organic compounds, PM10, PM2.5) associated with electricity, fuel use, and waste disposal.

Co-Benefits Risk Assessment (COBRA) Screening Model

COBRA is a screening tool that enables users to:

  • Roughly estimate the impact of emission changes on ambient air pollution
  • Further translate this into health effect impacts
  • Monetize the value of those impacts
  • View the estimated county-level results in tables and maps


E-Calc Exit EPA disclaimer is a Web-based calculator that allows government and building industry users to design and evaluate a wide range of projects for energy savings and emissions reduction potential. This tracking tool was developed by Texas A&M University's Energy Systems Laboratory in response to legislative incentives to quantify emissions reductions from building energy savings and distributed renewable technology. E-Calc evaluates residential, commercial, retail, and municipal buildings energy and emissions savings, as well as savings from renewables like solar heating, solar PV, and wind power.

Environmental Benefits Mapping and Analysis Program (BenMAP)

BenMAP is a tool for estimating the health and economic benefits of air pollution reduction strategies. It combines air pollution monitoring data, air quality modeling data, census information, and population projections to calculate a population's potential exposure to ambient air pollution. BenMAP is used primarily to estimate benefits from changes in particulate matter and ozone concentrations, but it can also be adapted for other pollutants. Most Windows-based computers run BenMAP.

OTC Workbook

The OTC Workbook Exit EPA disclaimer is a free tool developed for the Ozone Transport Commission to help local governments prioritize clean energy actions. The Workbook uses a detailed Microsoft Excel spreadsheet format based on electric power plant dispatch and on the energy savings of various measures to determine the air quality benefits of various actions taken in the OTC Region. This tool is simple, quick, and appropriate for scenario analysis. It can calculate predicted emission reductions from energy efficiency, renewables, energy portfolio standards (EPSs), and multi–pollutant proposals.

Power Profiler

States can use this tool to evaluate the environmental benefits of choosing cleaner sources of energy. The Power Profiler is a Web-based tool that allows users to evaluate the air pollution and greenhouse gas impact of their electricity choices. Using only a ZIP code, the tool generates a report describing the characteristics of one's electricity use.

Support Center for Regulatory Atmospheric Modeling (SCRAM)

EPA's SCRAM website provides descriptions and documentation for three types of air quality models: dispersion, photochemical, and receptor models; modeling guidance & support for applying air quality models for regulatory applications; and information on Meteorological data used in air quality models as derived from both ambient measurements and meteorological models.

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