U.S. Energy Overview
The major energy sources consumed in the United States are petroleum (oil), natural gas, coal, nuclear, and renewable energy. The major users are residential and commercial buildings, industry, transportation, and electric power generators. The pattern of fuel use varies widely by sector. For example, oil provides 92% of the energy used for transportation, but only about 1% of the energy used to generate electric power. Understanding the relationships between the different energy sources and their uses provides insights into many important energy issues.
How can we compare different fuels?Primary energy includes petroleum, natural gas, coal, nuclear fuel, and renewable energy. Electricity is a secondary energy source that is generated from these primary forms of energy.
Primary energy sources are commonly measured in different units: one barrel (equals 42 gallons) of oil, cubic feet of natural gas, tons of coal. To compare across fuels a common unit of measure is used. The United States uses British thermal unit, or Btus, which measure fuel use by the energy content of each fuel source.
Total U.S. energy use in 2013 was about 97.5 quadrillion Btus. One quadrillion equals 1015, or one thousand trillion. One quadrillion Btus, often referred to as a quad, therefore represents about 1% of total U.S. energy use.
In physical energy terms, one quad represents 172 million barrels of oil (about nine days of U.S. petroleum use), 51 million tons of coal (about 5.5% of total U.S. coal consumption in 2013), or 1 trillion cubic feet of dry natural gas (about 1.4% of total U.S. natural gas use in 2013).
The number of quads used in 2013 from each primary energy source is shown in the pie chart on the right. Petroleum accounts for the largest share of U.S. primary energy consumption, followed by natural gas, coal, renewable energy (including hydropower, wind, biomass, geothermal, and solar), and nuclear electric power.
Which primary energy sources are used in each sector?
Primary energy is used in residential and commercial buildings, in transportation, and by industry. Primary energy is also used to generate electricity. The bar chart on the right shows the amount of primary energy used in each of these sectors. As you can see, electric power generation is the largest user of primary energy, followed by transportation.
The electric power sector uses primary energy to generate electricity, which makes electricity a secondary, rather than a primary, energy source. Nearly all electricity is used in buildings and by industry. This means that the total amounts of energy used by residential and commercial buildings, industry, and transportation are actually higher than the amounts shown on the graphics when electricity is included.
The lines in the graphic below connecting the primary energy sources on the left with the demand sectors on the right summarize the links between energy sources and sectors in the United States. For example, because all nuclear energy is used in the electric power sector to generate electricity, and nuclear represents 22% of the primary energy used by that sector, the line between nuclear energy and the electric power sector shows 100% on the nuclear (supply source) side and 22% on the electric power (demand sector) side.
The mix of primary energy sources varies widely across demand sectors. Energy policies designed to influence the use of a particular primary fuel for environmental, economic, or energy security reasons often focus on sectors that are major users of that fuel.
For example, because 71% of petroleum is used in the transportation sector, where it provides 92% of the total energy used, policies to reduce oil consumption have tended to focus on the transportation sector. These policies usually seek to increase vehicle fuel efficiency or promote alternative fuels. About 91% of coal, but only 1% of petroleum, is used to generate electricity, which means that policies affecting electricity generation are likely to have a much larger impact on coal use than oil use.
Some primary energy sources, such as nuclear and coal, are entirely or predominately used in one sector. Others, like natural gas and renewables, are more evenly distributed across sectors. Similarly, while transportation is almost entirely dependent on one fuel (oil), electric power uses a variety of fuels.
Do sources and uses of energy change?
Linkages between fuels and sectors can and do change over time, but the change tends to occur slowly. For example, coal was once used extensively as a fuel for heating homes and commercial buildings, but that use of coal has decreased to almost nothing in the United States over the past half-century. Although renewable energy is still relatively small as a share of total primary energy in the transportation and electric power sectors, its role has been growing.
How dependent are we on foreign oil?
The United States relied on net imports (imports minus exports) for about 40% of the petroleum (crude oil and petroleum products) that we consumed in 2012. Just over half of these imports came from the Western Hemisphere. Our dependence on foreign petroleum has declined since peaking in 2005.
The United States consumed 18.6 million barrels per day (MMbd) of petroleum products during 2012, making us the world's largest petroleum consumer. The United States was third in crude oil production at 6.5 MMbd. Crude oil alone, however, does not constitute all U.S. petroleum supplies. Significant gains occur because crude oil expands in the refining process, liquid fuel is captured in the processing of natural gas, and we have other sources of liquid fuel, including biofuels. These additional supplies totaled 4.8 MMbd in 2012.
The United States imported 11.0 MMbd of crude oil and refined petroleum products in 2012. We also exported 3.2 MMbd of crude oil and petroleum products, so our net imports (imports minus exports) equaled 7.4 MMbd.
In 2012, the United States imported 2.1 MMbd of petroleum products such as gasoline, diesel fuel, heating oil, jet fuel, and other products while exporting 3.1 MMbd of products, making the United States a net exporter of petroleum products.
Over half of U.S. petroleum imports come from the Western Hemisphere Some may be surprised to learn that over 50% of U.S. crude oil and petroleum products imports came from the Western Hemisphere (North, South, and Central America, and the Caribbean, including U.S. territories) during 2012. About 29% of our imports of crude oil and petroleum products came from the Persian Gulf countries of Bahrain, Iraq, Kuwait, Qatar, Saudi Arabia, and United Arab Emirates. Our largest sources of net crude oil and petroleum product imports were Canada and Saudi Arabia.
Top sources of net crude oil and petroleum product imports:
Reliance on petroleum imports has declined U.S. dependence on imported oil has declined since peaking in 2005. This trend is the result of a variety of factors including a decline in consumption and shifts in supply patterns.1 The economic downturn after the financial crisis of 2008, improvements in efficiency, changes in consumer behavior, and patterns of economic growth all contributed to the decline in petroleum consumption. At the same time, increased use of domestic biofuels (ethanol and biodiesel), and strong gains in domestic production of crude oil and natural gas plant liquids expanded domestic supplies and reduced the need for imports
What is the role of coal in the United States?
The United States holds the world's largest estimated recoverable reserves of coal and is a net exporter of coal. In 2013, U.S. coal mines produced just under one billion short tons of coal, the lowest output level since 1993. More than 90% of this coal was used by U.S. power plants to generate electricity. While coal has been the largest source of electricity generation in the United States for over 60 years, its annual share of total net generation declined from nearly 50% in 2007 to 39% in 2013 as some power producers switched to more competitively priced natural gas. At the same time, new environmental regulations also made it more costly to operate some coal plants.
Coal is an abundant U.S. resourceThe United States is home to the largest estimated recoverable reserves of coal in the world. In fact, we have enough estimated recoverable reserves of coal to last more than 200 years, based on current production levels. Coal is produced in 25 states spread across three major coal-producing regions. In 2013, approximately 70% of production originated in five states: Wyoming, West Virginia, Kentucky, Pennsylvania, and Illinois.
Most U.S. coal is used to generate electricity
About 93% of the coal consumed in the United States is used for generating electricity. The United States has around 1,300 coal-fired electricity generating units in operation at almost 560 plants across the country. Together, these power plants consumed more than 858 million short tons of coal to generate 39% of the electricity produced in the United States during 2013.
Although coal-fired generation still holds the largest share among all sources of electricity, its use has declined since 2007 due to a combination of slow growth in electricity demand, strong price competition with natural gas, increased use of renewable technologies, and new environmental regulations. See related article—Today in Energy, July 6, 2012.
While the share of total net electricity generated from coal in the United States is expected to decrease by 2040, coal is still expected to remain an important fuel in generating electricity in the United States in the absence of policies designed to reduce emissions of carbon dioxide and other greenhouse gases. However, the implementation of new policies to limit carbon dioxide emissions from power generation could significantly change the outlook for the use of coal in generating electricity.
Besides its role in generating electricity, coal also has industrial applications such as in cement production and coke conversion for the smelting of iron ore at blast furnaces used to make steel. A small amount of coal is also burned to heat commercial, military, and institutional facilities, and an even smaller amount is used to heat homes.
The United States exports coal to other countries
Between 2000 and 2012, about 5% of the coal produced in the United States, on average, was exported to other countries. In 2013, the share of U.S. coal production that was exported increased to 12%, totaling 117.7 million short tons. However, the overall volume of coal exports declined by 6% from 125.7 million short tons in 2012.
Europe and Asia continue to be the top destinations for U.S. coal exports. Coal exports come in two forms:
•Metallurgical coal, which can be used for steel production
The United States also imports a small amount of coal, with most of it coming from Colombia. Some coal electric generating units along the Gulf Coast and the Atlantic Coast find it cheaper to import coal from other nations than to have domestic coal transported by rail or barge from the coal-producing regions of the United States.
Coal is a relatively inexpensive fuel
Although some natural gas plants are more efficient than coal plants at generating electricity, in the past the fuel cost of generating one kilowatthour of electricity from natural gas had typically been higher than that of coal. However, coal began losing its price advantage over natural gas for electricity generation in some parts of the country in 2009, particularly in the eastern United States. A surge in natural gas production from U.S. shale deposits substantially reduced the price of natural gas, thus making it more competitive for use in generating electricity. See related article—Today in Energy, May 23, 2013.
Environmental effects from using coal
The mining of coal can have a negative impact on ecosystems and water quality. When coal is burned it produces several types of emissions that adversely affect the environment and human health. Coal emits sulfur dioxide, nitrogen oxide, heavy metals (such as mercury and arsenic), and acid gases (such as hydrogen chloride), which have been linked to acid rain, smog, and other environmental and health-related concerns. Coal also emits carbon dioxide, the greenhouse gas most responsible for global warming. In 2013, coal accounted for 32% of the energy-related carbon dioxide emissions in the United States
Outlook for future coal useThe economics of burning coal may change if the United States adopts policies that restrict or otherwise control carbon dioxide (CO2) emissions.
In January 2014, the U.S. Environmental Protection Agency (EPA) issued a revised new source performance standard proposal for emissions of CO2 that requires new coal-fired power plants to limit their emissions to 1,100 pounds of CO2 per megawatthour. The proposed emission limit would effectively require that new coal-fired electric generating units employ carbon capture and sequestration (CCS) technologies to reduce uncontrolled emissions of CO2 by approximately 50%.
For existing power plants, in June 2014 the EPA released proposed rules designed to cut CO2 emissions at current coal-fired electric generating units 30% from 2005 levels by the year 2030.
CCS would theoretically address much of coal's carbon dioxide emissions. However, substantial economic and technological hurdles for CCS remain.
In March 2013, the EPA finalized the Mercury and Air Toxics Standards to reduce emissions of mercury and other air toxics from new and existing coal and oil-fired electric generating units. Power plants are responsible for more mercury emissions than any other man-made source. See related article—Today in Energy, March 28, 2014. The standards were challenged in court, but they were upheld by a federal appeals court in April 2014.
Separately, recent further efforts to control nitrogen oxide (NOx) and sulfur dioxide (SO2) emissions from power plants could also have an effect on the use of coal in electricity generation. The EPA's Cross-State Air Pollution Rule (CSAPR), finalized in July 2011, seeks to reduce SO2 and NOx emissions from power plants in 28 states. The rule was challenged, but in April 2014 the U.S. Supreme Court upheld CSAPR.