Energy in Briefs explain important energy topics in plain language. Each Brief answers a question relevant to the public and recommends resources for further reading. Please use the tools to the right to give us feedback, share with others, or sign up for notices as new Briefs are released.

  • Libby  hydroelectric plant
    August 29, 2012

    What is the role of hydroelectric power in the United States?

    The importance of hydropower as a source of electricity generation varies by geographic region. While hydropower accounted for 8% of total U.S. electricity generation in 2011, it provided over half of the electricity in the Pacific Northwest. Because hydroelectric generation relies on precipitation, it varies widely from month to month and year to year.

  • Photo of a refinery
    July 27, 2012

    What's changing in East Coast fuels markets?

    The U.S. East Coast petroleum product market is undergoing fundamental changes from the standpoint of supply and demand. In addition to the announced idling and potential closure of several major refineries, a number of Northeastern states plan a transition to ultra-low sulfur diesel for heating oil use beginning with New York in the summer of 2012. This article provides an overview of EIA's recent analyses related to East Coast fuels markets.

  • Hands holding lumps of coal
    July 18, 2012

    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 2011, our nation's coal mines produced more than a billion short tons of coal, and more than 90% of this coal was used by U.S. power plants to generate electricity.

  • oil tanker
    July 13, 2012

    How dependent are we on foreign oil?

    The United States relied on net imports (imports minus exports) for about 45% of the petroleum (crude oil and petroleum products) that we consumed in 2011. Just over half of these imports came from the Western Hemisphere. Our dependence on foreign petroleum has declined since peaking in 2005.

  • shale gas
    July 9, 2012

    What is shale gas and why is it important?

    Shale gas refers to natural gas that is trapped within shale formations. Shales are fine-grained sedimentary rocks that can be rich sources of petroleum and natural gas. Over the past decade, the combination of horizontal drilling and hydraulic fracturing has allowed access to large volumes of shale gas that were previously uneconomical to produce. The production of natural gas from shale formations has rejuvenated the natural gas industry in the United States.

  • wind turbine
    June 27, 2012

    How much of our electricity is generated from renewable sources?

    U.S. power plants used renewable energy sources — water (hydroelectric), wood, wind, organic waste, geothermal, and sun — to generate about 13% of our electricity in 2011.

  • greenhouse
    June 21, 2012

    What are greenhouse gases and how much are emitted by the United States?

    Greenhouse gases trap heat from the sun and warm the planet's surface. Of U.S. greenhouse gas emissions, the majority are related to energy consumption, and most of those are carbon dioxide. From 1990 to 2011, energy-related carbon dioxide emissions in the United States increased by about 0.4% per year. The United States produced about 18% of the world's total energy-related carbon dioxide in 2010 — the last year for which comparable data are available.

  • Atom with electron paths
    June 11, 2012

    What is the status of the U.S. nuclear industry?

    There are currently 104 operable commercial nuclear reactors at 65 nuclear power plants. Since 1990, the share of the Nation's total electricity supply provided by nuclear power generation has averaged about 20%, with increases in nuclear generation that have roughly tracked the growth in total electricity output. Partly in response to incentives provided by the Energy Policy Act of 2005, including new construction loan guarantees for new nuclear power plants, EIA expects nuclear power output to grow, although at a rate about half that of total electricity generation.

  • Puzzle pieces showing an energy source and user.
    May 18, 2012

    What are the major sources and users of energy in the United States?

    The major energy sources 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 93% 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.

  • High voltage sign
    April 27, 2012

    What is the electric power grid, and what are some challenges it faces?

    The grid of electric power lines has evolved into three large interconnected systems that move electricity around the country. Standards have been developed by the electric power industry to ensure coordination for the linked operations. Challenges facing the power grid include getting approval for corridors of land for new transmission lines within states or that cross multiple states, and the financing and constructing of new transmission lines to assure continued reliability of our electricity supply.

  • Photo of a matchbox with colored match heads
    March 19, 2012

    How can we compare or add up our energy consumption?

    To compare or aggregate energy consumption across different energy sources like oil, natural gas, and electricity, we must use a common unit of measure. This is similar to calculating your food energy intake by adding up the calories in whatever you eat.

  • Oil drop containing the world
    March 15, 2012

    Who are the major players supplying the world oil market?

    The world oil market is complicated. Companies are often thought of as the primary actors in this market, but governments play a large role as well. To answer this question, we'll explore the role oil companies and governments play in the world oil market and their interactions.

  • Carbon dioxide molecule model
    March 13, 2012

    What is a cap-and-trade program and how does it work?

    A cap-and-trade program is designed to reduce emissions of a pollutant by placing a limit (or cap) on the total amount of emissions. The cap is implemented through a system of allowances that can be traded to minimize costs to affected sources. Cap-and-trade programs for greenhouse gas emissions would increase the costs of using fossil fuels.

  • Stock chart screen
    February 14, 2012

    What were the key energy commodity price trends in 2011?

    Energy commodity price trends varied widely during 2011. Crude oil and petroleum products prices increased during 2011, while natural gas, coal, and electricity prices declined. This article provides an overview of key energy commodity price trends in 2011 based on prices seen in futures markets.

  • Electricity transmission lines and windmill
    January 23, 2012

    What are renewable portfolio standards (RPS) and how do they affect renewable electricity generation?

    Renewable portfolio standards (RPS) are policies designed to increase electricity generation from renewable resources, including wind, solar, geothermal, and biomass. While there is no National-level renewable portfolio standard, many States have set renewable portfolio standards.

  • a row of wind turbines
    August 30, 2011

    How much of the world's electricity supply is generated from wind and who are the leading generators?

    Worldwide wind power generation exceeded 250 billion kilowatthours in 2009, which is equivalent to the annual electricity consumption of over 22 million average households in the United States. Wind generation increased by about 20% from 2008 to 2009, and has more than tripled since 2004. This growth is mostly due to capacity increases in the United States, China, India, and Western Europe. Despite this growth, the world still generated only 1% of its total electricity from wind power in 2009.

  • electric power generator
    August 8, 2011

    How old are U.S. power plants?

    The current fleet of electric power generators has a wide range of ages. About 530 gigawatts, or 51% of all generating capacity, were at least 30 years old at the end of 2010. Trends in generating capacity additions vary by fuel type, for coal, hydropower, natural gas, nuclear, petroleum, and wind.