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Climate Change

Sources of Greenhouse Gas Emissions

Electricity Sector Emissions

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Total U.S. Greenhouse Gas Emissions by Economic Sector in 2014
Pie chart of total U.S. greenhouse gas emissions by economic sector in 2014. 30 percent is from electricity, 26 percent is from transportation, 21 percent is from industry, 12 percent is from commercial and residential, and 9 percent is from agriculture.

Total Emissions in 2014 = 6,870 Million Metric Tons of CO2 equivalent
* Land Use, Land-Use Change, and Forestry in the United States is a net sink and offsets approximately 11% of these greenhouse gas emissions.
All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2014

The Electricity sector involves the generation, transmission, and distribution of electricity. Carbon dioxide (CO2) makes up the vast majority of greenhouse gas emissions from the sector, but smaller amounts of methane (CH4) and nitrous oxide (N2O) are also emitted. These gases are released during the combustion of fossil fuels, such as coal, oil, and natural gas, to produce electricity. Less than 1% of greenhouse gas emissions from the sector come from sulfur hexafluoride (SF6), an insulating chemical used in electricity transmission and distribution equipment.

Greenhouse Gas Emissions in the Electricity Sector by Fuel Source

Coal combustion is generally more carbon intensive than burning natural gas or petroleum for electricity. Although coal accounts for about 77% of CO2 emissions from the sector, it represents about 39% of the electricity generated in the United States. About 27% of electricity generated in 2014 was generated using natural gas, an increase relative to 2013. Petroleum accounts for approximately 1% of electricity generation. The remaining generation comes from nuclear (about 19%) and renewable sources (about 13%), which includes hydroelectricity, biomass, wind, and solar.[1] These other sources usually release fewer greenhouse gas emissions than fossil fuel combustion, if any emissions at all.

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In 2014, the electricity sector was the largest source of U.S. greenhouse gas emissions, accounting for about 30% of the U.S. total. Greenhouse gas emissions from electricity have increased by about 12% since 1990 as electricity demand has grown and fossil fuels have remained the dominant source for generation.

To learn about projected greenhouse gas emissions to 2020, visit the U.S. Climate Action Report 2014 (PDF) (310 pp., 23.1 MB).

Greenhouse Gas Emissions from Electricity
Line graph of greenhouse gas emissions from the electricity sector for 1990 to 2014. The greenhouse gas emissions started around 1,800 million metric tons of carbon dioxide equivalents in 1990, and rose to a peak of just below 2,500 million around 2007. At the end of the time span, the line starts to dip and ends around 2,080 million metric tons of carbon dioxide equivalents in 2014.

Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2014.

Total U.S. Greenhouse Gas Emissions by Sector with Electricity Distributed
Pie chart showing total U.S. Greenhouse Gas Emissions by Sector with Electricity Distributed. 34 percent is from Residential and Commercial, 29 percent is from industry, 26 percent is from transportation, and 10 percent is from agriculture.

Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2014.

Greenhouse Gas Emissions by Electricity End-Use

Electricity is consumed by other sectors--in homes, businesses, and factories. Therefore, it is possible to attribute the greenhouse gas emissions from electricity production to the sectors that use the electricity. Looking at greenhouse gas emissions by end-use sector can help us understand energy demand across sectors and changes in energy use over time.

When emissions from electricity are allocated to the end-use sector, industrial activities account for a much larger share of U.S. greenhouse gas emissions. Emissions from commercial and residential buildings also increase substantially when emissions from electricity are included, due to their relatively large share of electricity consumption (e.g., lighting and appliances).

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Reducing Emissions from Electricity

There are a variety of opportunities to reduce greenhouse gas emissions associated with electricity generation, transmission, and distribution. The table shown below categorizes these opportunities and provides examples. For a more comprehensive list, see Chapter 7 of the Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (PDF) (139 pp, 7.5MB).Link to EPA's External Link Disclaimer

Under the President's Climate Action Plan, EPA is taking action to reduce emissions from power plants. Learn More

Example Reduction Opportunities for the Electricity Sector
Type How Emissions are Reduced Examples
Increased Efficiency of Power Plants and Fuel Switching Increasing efficiency of existing power plants by using advanced technologies or substituting fuels that combust more efficiently.
  • Converting a conventional coal-powered steam turbine into an advanced turbine that uses pulverized coal.
  • Converting a coal-powered turbine into a natural gas-powered turbine.
  • Converting a single-cycle turbine into a combined-cycle turbine.
Renewable Energy Using renewable energy sources rather than fossil fuel to generate electricity. Increasing the share of total electricity generated from wind, solar, hydro, and geothermal sources and from certain biofuel sources.
Increased Energy Efficiency (end-use) Reducing energy demand by increasing efficiency and conservation in homes, businesses, and industry. EPA's ENERGY STAR® partners removed over 300 million metric tons of greenhouse gases in 2014 alone, and saved consumers and businesses over $34 billion on their utility bills.
Nuclear Energy Generating electricity from nuclear processes rather than the combustion of fossil fuels. Building nuclear power plants as fossil fuel power plants are retired.
Carbon Capture Sequestration and Storage (CCS) Capturing CO2 as a by-product of fossil fuel combustion before it enters the atmosphere and then transferring the CO2 to a long-term storage area, such as an underground geologic formation. Capturing CO2 from the stacks of a coal-fired power plant, and then transferring the CO2 via pipeline to a nearby abandoned oil field where the CO2 is injected underground. Learn more about CCS.


  1. U.S. Energy Information Administration (2014). Electricity Explained - Basics.

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6,870 million metric tons of CO2 equivalent--what does that mean?

An Explanation of Units

A million metric tons is equal to about 2.2 billion pounds, or 1 trillion grams. For comparison, a small car is likely to weigh a little more than 1 metric ton. Thus, a million metric tons is roughly the same mass as 1 million small cars!

The U.S. Inventory uses metric units for consistency and comparability with other countries. For reference, a metric ton is a little bit larger (about 10%) than a U.S. "short" ton.

GHG emissions are often measured in carbon dioxide (CO2) equivalent. To convert emissions of a gas into CO2 equivalent, its emissions are multiplied by the gas's Global Warming Potential (GWP). The GWP takes into account the fact that many gases are more effective at warming Earth than CO2, per unit mass.

The GWP values appearing in the Emissions webpages reflect the values used in the U.S. Inventory, which are drawn from the IPCC’s Fourth Assessment Report (AR4). For further discussion of GWPs and an estimate of GHG emissions using updated GWPs, see Annex 6 of the U.S. Inventory and the IPCC's discussion on GWPs. Link to EPA's External Link Disclaimer

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