The United States has been an integral part of the global energy sector for many decades. It is a global leader in energy production, consumption, and technology, and its energy market is highly sophisticated. Its energy prices, for the most part, are determined in the marketplace and rise or fall with changes in supply and demand. The United States is a major producer of all forms of energy—oil, natural gas, coal, nuclear power, and renewable energy. Since the beginning of the 21 st century, the U.S. energy sector has transformed from a situation of declining production, especially of oil and natural gas, to one in which the United States is a growing producer. Exports of energy are rising while imports are falling. Prices, technology, and regulations have prompted changes in the energy mix. This report provides an overview of U.S. energy issues, and it serves as an initial resource document for related information, data, and CRS contacts. The report is organized around the major fuels and energy sources used in the United States. It also highlights the role of the federal government, particularly the use of federal lands in energy production. It does not focus on energy infrastructure, security, research and development, energy efficiency, or environmental issues, although those areas are also critical to the U.S. energy sector. Energy policy in the United States has generally focused on three major goals: assuring a secure supply of energy, keeping energy costs low, and protecting the environment. In pursuit of those goals, government programs have been developed to improve energy efficiency, to promote the domestic production of conventional energy sources, and to develop new energy sources, including advanced nuclear and renewable energy sources. Implementing these programs sometimes has been controversial because of the varying importance given to different aspects of energy policy by different stakeholders. For some, dependence on imports of energy, particularly from the Persian Gulf, is the primary concern; for others, the continued use of fossil fuels, whatever their origin, is of greatest concern. The extent to which human-induced global climate change warrants changing U.S. energy policy to reduce the production and use of fossil fuels is particularly controversial. Another dichotomy is between those who see government intervention in the energy sector as a positive force, and those who do not and seek to restrict government intervention as much as possible. Energy policy has often been legislated in large, complex bills that deal with a wide variety of issues, with debate spanning several sessions. The Energy Policy Act of 2005 (EPAct 2005; P.L. 109-58 ) was the most recent comprehensive general legislation, with provisions and authorizations in almost all areas of energy policy. The Energy Independence and Security Act of 2007 (EISA, P.L. 110-140 ) set new target fuel economy standards for cars and light trucks of 35 miles per gallon by 2020, and expanded the renewable fuels standard (RFS) to require 9.0 billion gallons of biofuels in transportation in 2008 (equivalent to 600,000 barrels per day), rising to 36 billion gallons by 2022 (equivalent to 2.4 million barrels per day). EISA also included energy efficiency standards for appliances and other equipment, and provisions on industrial and building efficiency, which have continued to be of interest in the 115 th Congress. In the 114 th Congress, both the House and Senate considered broad energy legislation, as well as specific topics of key interest. The two primary bills were S. 2012 , the Energy Policy and Modernization Act, and H.R. 8 , the North American Energy Security and Infrastructure Act of 2015. After the House passed S. 2012 with the text of H.R. 8 , a conference committee met to consider the two versions of S. 2012 but did not resolve the differences before the 114 th Congress adjourned. Both bills addressed a variety of energy topics, including energy efficiency in federal buildings, data centers, manufacturing, and schools; water conservation/efficiency; regulation and development of nonfederal hydropower; electric grid cybersecurity; and review of the Strategic Petroleum Reserve (SPR). In the 115 th Congress, a range of energy bills have been proposed. Most notably, the Arctic National Wildlife Refuge (ANWR) was opened to oil and gas development under the 2017 tax revision ( P.L. 115-97 ). The law directs the Secretary of the Interior to establish an oil and gas leasing program in ANWR's coastal plain. Other energy-related bills have been introduced, including S. 1460 , the Energy and Natural Resources Act of 2017. S. 1460 includes provisions on energy efficiency, energy and minerals supply, and energy infrastructure, among other provisions. (Many of the provisions in S. 1460 are similar or identical to provisions in the Senate version of S. 2012 in the 114 th Congress.) The Senate Committee on Energy and Natural Resources held hearings on the bill in September 2017, but no further action has been taken. Other bills in the 115 th Congress include House-passed bills to require federal agencies to coordinate on energy-efficient information technology ( H.R. 306 ), assist states with emergency energy planning ( H.R. 3050 ), and temporarily store nuclear waste ( H.R. 3053 ). The United States is the second largest producer and consumer of energy in the world, behind China. U.S. primary energy consumption (see Figure 1 ) has held relatively steady since 2000, falling 1%; however, the fuel mix has changed. While oil has remained at almost 40% of the fuel mix, natural gas and renewables have increased in both percentage and absolute terms at the expense of coal. Nuclear generation has stayed flat. The change in the U.S. fuel mix has centered on the electricity sector where there are fuel substitutes (see " The Electric Power Sector "). Electric power generation in 2017 came from coal (30%), natural gas (32%), nuclear (20%), renewables (17%), and petroleum (<1%), according the U.S. Energy Information Administration (EIA). This is a significant change from 2000, when coal accounted for 52% of the electricity fuel mix and natural gas was 16%, nuclear was still almost 20%, and renewables were 9%. Industrial use of energy has also experienced changes, but not to the same degree as electric power generation in recent years. On the other end of the spectrum, energy in transportation is dominated by petroleum, which made up 92% of the fuel used in transportation in 2017, down from 97% in 2000. U.S. energy production between 2000 and 2017 increased 23%, a significant amount, especially considering that historically the United States was viewed as a growing importer of energy. (See Figure 1 .) Renewable energy production has increased by 83% during the time frame, the largest increase of all fuel types. Oil production has risen the next fastest, growing 64%, followed by natural gas production at 42%. The increase in production of both these resources comes from innovations in extraction from unconventional (or tight ) formations, such as shale (see text box below, "Shale Resources Make the Difference"). Coal production, on the other hand, has declined during the time period by about 31%. Federal lands account for a significant amount of total U.S. energy production. For example, in 2017, as a percentage of total U.S. energy production, approximately 24% of crude oil and 13% of natural gas gross withdrawals came from federal lands. In 2016 (the latest year for this data), 40% of coal came from federal lands. Weighing energy production on federal lands against other resource values has long been a fundamental question for Congress. Much of the onshore federal estate is open to energy and mineral exploration and development, including Bureau of Land Management (BLM) and many Forest Service (FS) lands. However, many National Park Service (NPS) lands and areas within the National Wilderness Preservation System, as well as certain other federal lands, have been specifically withdrawn from exploration and development. One previously withdrawn area—the Arctic National Wildlife Refuge—was recently opened to oil and gas development under the Tax Cuts and Jobs Act ( P.L. 115-97 ). The law directs the Secretary of the Interior to establish an oil and gas leasing program in ANWR's coastal plain. Development of oil, natural gas, and coal on federal lands is governed primarily by the Mineral Leasing Act of 1920 (MLA). Geothermal leasing on federal lands is conducted under the authority of the Geothermal Steam Act of 1970, as amended. Development of solar and wind energy sources on BLM and FS lands is governed primarily by right-of-way authorities under Title V of the Federal Land Policy and Management Act (FLPMA). Offshore federal resources, within and beyond the U.S. Exclusive Economic Zone (EEZ), are also open for exploration and development. The federal government is responsible for managing energy resources in approximately 1.7 billion acres of waters belonging to the United States. These offshore resources are governed by the Outer Continental Shelf Lands Act of 1953 (OCSLA), as amended. Federal lands also are available for renewable energy projects. BLM manages the solar and wind energy programs on about 20 million acres for each program and has the authority to manage about 240 million acres for geothermal leasing on federal lands. Geothermal capacity on federal lands represents 40% of U.S. total geothermal electric generating capacity. Oil production fluctuated year-to-year on federal lands from 2008 to 2017 but overall it increased by 47% over the 10-year period. However, because crude oil production on nonfederal lands doubled over the decade (primarily due to improved extraction technology, favorable geology, and the ease of leasing), the share of total U.S. crude oil production from federal lands fell from its peak of nearly 36% in 2009 and 2010 to about 24% in 2017.