Glossary

Biomass is organic nonfossil material of biological origin constituting a renewable energy source.

A British thermal unit (Btu) is a measure of the heat content of fuels or energy sources. It is the quantity of heat required to raise the temperature of one pound of liquid water by 1 degree Fahrenheit at the temperature that water has its greatest density (approximately 39 degrees Fahrenheit).

Coal is a readily combustible black or brownish-black rock whose composition, including inherent moisture, consists of more than 50 percent by weight and more than 70 percent by volume of carbonaceous material. It is formed from plant remains that have been compacted, hardened, chemically altered, and metamorphosed by heat and pressure over geologic time.

The commercial sector is an energy-consuming sector that consists of service-providing facilities and equipment of businesses; Federal, State, and local governments; and other private and public organizations, such as religious, social, or fraternal groups. The commercial sector includes institutional living quarters. It also includes sewage treatment facilities. Common uses of energy associated with this sector include space heating, water heating, air conditioning, lighting, refrigeration, cooking, and running a wide variety of other equipment. Note: This sector includes generators that produce electricity and/or useful thermal output primarily to support the activities of the above-mentioned commercial establishments.

A cooperative electric utility is one that is legally established to be owned by and operated for the benefit of those using its service. The utility company will generate, transmit, and/or distribute supplies of electric energy to a specified area not being serviced by another utility. Such ventures are generally exempt from Federal income tax laws.

An electric utility is a corporation, person, agency, authority, or other legal entity or instrumentality aligned with distribution facilities for delivery of electric energy for use primarily by the public.

Electricity generation is the amount of electric energy produced, expressed in kilowatt-hours or megawatt-hours.

The electricity generation capacity, or generator nameplate capacity (installed) is the maximum rated output of a generator, prime mover, or other electric power production equipment under specific conditions designated by the manufacturer. Installed generator nameplate capacity is commonly expressed in megawatts (MW) and is usually indicated on a nameplate physically attached to the generator.

In general, the emissions rate refers to the weight of pollutant emitted per unit of time. For utilities, the emissions rate refers to the weight of pollutant per megawatt-hour.

An end-use sector refers to a sector that consumes primary energy and electricity (a secondary energy source) produced by the electric power sector. The transportation, industrial, commercial, and residential sectors are considered end-use sectors. Total energy consumption by the end-use sectors includes their primary energy use, purchased electricity, and electrical system energy losses (energy conversion and other losses associated with the generation, transmission, and distribution of purchased electricity) and other energy losses.

An energy flow tracks energy from primary energy resource to consumption.

An energy resource, or energy source, is any substance or natural phenomenon that can be consumed or transformed to supply heat or power. Examples include petroleum, coal, natural gas, nuclear, biomass, electricity, wind, sunlight, geothermal, water movement, and hydrogen in fuel cells.

A fossil fuel is an energy source formed in the Earth's crust from decayed organic material. The common fossil fuels are petroleum, coal, and natural gas.

Fossil fuel combustion is the burning of fossil fuels to produce energy.

Fuel refers to any material substance that can be consumed to supply heat or power, including fossil fuels (petroleum, coal, and natural gas), and other consumable materials, such as uranium, biomass, and hydrogen.

GHG emissions refers to any emissions from GHGs, or greenhouse gases: Gases that are transparent to solar (short-wave) radiation but opaque to long-wave (infrared) radiation, thus preventing long-wave radiant energy from leaving Earth's atmosphere. The net effect is a trapping of absorbed radiation and a tendency to warm the planet's surface.

Geothermal energy refers to using hot water or steam extracted from geothermal reservoirs in the earth's crust. Water or steam extracted from geothermal reservoirs can be used for geothermal heat pumps, water heating, or electricity generation.

Hydroelectric power refers to the use of flowing water to produce electrical energy.

The industrial sector is an energy-consuming sector that consists of all facilities and equipment used for producing, processing, or assembling goods. The industrial sector encompasses the following types of activity manufacturing (NAICS codes 31-33); agriculture, forestry, fishing and hunting (NAICS code 11); mining, including oil and gas extraction (NAICS code 21); and construction (NAICS code 23). Overall energy use in this sector is largely for process heat and cooling and powering machinery, with lesser amounts used for facility heating, air conditioning, and lighting. Fossil fuels are also used as raw material inputs to manufactured products. Note: This sector includes generators that produce electricity and/or useful thermal output primarily to support the above-mentioned industrial activities. Various EIA programs differ in sectoral coverage.

An IOU is a privately-owned electric utility whose stock is publicly traded. It is rate regulated and authorized to achieve an allowed rate of return.

The EPA defines a "large emitting facility" as one that emits 25,000 metric tons or more of carbon dioxide equivalent per year. These facilities are required to report emissions to the EPA through the Greenhouse Gas Reporting Program (GHGRP).

MMT CO₂ is a unit commonly used to measure emissions and means one million metric tons of carbon dioxide. MT CO₂ is one metric ton of carbon dioxide.

A megawatt-hour is a unit used to measure electricity generation and is equivalent to one thousand kilowatt-hours or one million watt-hours.

A megawatt is a unit used to measure electricity generation capacity and is equivalent to one million watts of electricity.

Municipal utilities and other publicly-owned utilities are nonprofit government entities that serve at either the local or the state level. Municipal utilities are owned and operated by local communities and often operate within the local municipal public works department. This class of utility is often not regulated by state or federal agencies, and municipalities may operate the utility as a tool to promote local economic expansion or lower local tax burdens.

The nameplate capacity is the maximum electric output an electricity generator can produce under specific conditions. Installed generator nameplate capacity is commonly expressed in megawatts (MW) and is usually indicated on a nameplate physically attached to the generator.

Natural gas is a gaseous mixture of hydrocarbon compounds, the primary one being methane.

Net electricity generation is the amount of gross generation less the electrical energy consumed at the generating station(s) for station service or auxiliaries.

Non-fossil energy refers to energy resources not from fossil fuels. A fossil fuel is an energy source formed in the Earth's crust from decayed organic material. The common fossil fuels are petroleum, coal, and natural gas.

Petroleum is a broadly defined class of liquid hydrocarbon mixtures. Included are crude oil, lease condensate, unfinished oils, refined products obtained from the processing of crude oil, and natural gas plant liquids. Note: Volumes of finished petroleum products include non hydrocarbon compounds, such as additives and detergents, after they have been blended into the products.

An electric power plant is a station containing prime movers, electric generators, and auxiliary equipment for converting mechanical, chemical, and/or fission energy into electric energy.

PUDs are municipal corporations organized to provide electric service to both incorporated cities and towns and unincorporated rural areas.

The residential sector is an energy-consuming sector that consists of living quarters for private households. Common uses of energy associated with this sector include space heating, water heating, air conditioning, lighting, refrigeration, cooking, and running a variety of other appliances. The residential sector excludes institutional living quarters. Note: Various EIA programs differ in sectoral coverage.

Sectoral greenhouse gas emissions refer to greenhouse gas emissions by use sector (residential, commercial, industrial, transportation, and electric power).

Solar energy is the radiant energy of the sun, which can be converted into other forms of energy, such as heat or electricity.

Surplus electricity is energy generated that is beyond the immediate needs of the producing system. This energy may be supplied by spinning reserve and sold on an interruptible basis.

TBtu = Trillions of British thermal units.  British thermal unit (Btu) is a measure of the heat content of fuels or energy sources. It is the quantity of heat required to raise the temperature of one pound of liquid water by 1 degree Fahrenheit at the temperature that water has its greatest density (approximately 39 degrees Fahrenheit).

The transportation sector is an energy-consuming sector that consists of all vehicles whose primary purpose is transporting people and/or goods from one physical location to another. Included are automobiles; trucks; buses; motorcycles; trains, subways, and other rail vehicles; aircraft; and ships, barges, and other waterborne vehicles. Vehicles whose primary purpose is not transportation (e.g., construction cranes and bulldozers, farming vehicles, and warehouse tractors and forklifts) are classified in the sector of their primary use. Note: Various EIA programs differ in sectoral coverage.

Waste energy is energy that is not harnessed. This includes energy lost as heat during combustion or transformation into electricity, transmission losses, and other factors.

Wind energy is kinetic energy present in wind motion that can be converted to mechanical energy for driving pumps, mills, and electric power generators.