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Energy Intensity Indicators: Terminology and Definitions

The Energy Intensity Indicators Web site uses the following terms with their associated definitions.

Primary Energy
Primary energy consumption is the amount of fossil and renewable fuels directly consumed by either one of the four major end-use sectors or by the electric power sector. The total primary energy across these five sectors is consistent with total energy use in the economy as shown in Table 2.1a of the Energy Information Administration's (EIA's) Annual Energy Review (AER) (see the EIA Annual Energy Review).
Delivered Energy
(see Highlights - Delivered Energy) The amount of energy consumed at the point of sale (e.g., that enters the home, building, or establishment) without adjustment for energy loss in the generation, transmission, and distribution of energy. This is primary energy for the four end-use sectors plus electricity sales. Delivered energy is, sometimes referred to as "site" energy (see the EIA Residential Glossary).
Source Energy
(see Highlights - Source Energy) Source energy consumption is the amount of fossil and renewable fuels consumed for the four end-use sectors, plus the electricity used by these end-use sectors (electricity sales). In addition, the losses associated with the production of electricity by the utility sector (i.e., losses that occur in the generation, transmission, and distribution) are also allocated to the end-use sectors. The sum of source energy for four end-use sectors (transportation, industrial, residential buildings, and commercial buildings) is equal to the sum of all primary energy consumed by the four sectors plus energy consumed by the electricity producing sector. "Source energy" is equivalent to the term "total energy" as used by EIA in the AER. For this Web site, the use of the term "source" was judged to be more precised, particularly in discussions involving subsectors and aggregations of subsectors where the team total energy may be ambiguous.
Energy Efficiency
Energy efficiency can be defined for a component or service as the amount of energy required in the production of that component or service; for example, the amount of steel that can be produced with one billion Btu of energy. Energy efficiency is improved when a given level of service is provided with reduced amounts of energy inputs, or services or products are increased for a given amount of energy input.
Energy Intensity
The amount of energy used in producing a given level of output or activity (see also Energy Efficiency vs. Energy Intensity). It is measured by the quantity of energy required to perform a particular activity (service), expressed as energy per unit of output or activity measure of service.
Economy-wide energy intensity
(also referred to as aggregate energy intensity). This is the energy intensity of the entire U.S. economy. It is the aggregate of the intensity of the four major energy consuming end-use sectors (transportation, industrial, residential buildings, and commercial buildings) and the electricity producing sector.
Sector energy intensity
This is energy intensity calculated at the sector level. When primary energy is considered, intensity is calculated for five sectors, the four end-use sectors and the electricity producing sector. When total energy is considered intensity is calculated for the four end-use sectors only.
Subsector energy intensity
This is the energy intensity for subsectors within a given sector (See subsectors). Subsector intensity is energy use divided by the activity of the subsector.
End-Use sectors
The four sectors that consume primary energy and electricity: transportation, industry, residential building and commercial buildings.
Transportation sector
An end-use 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. (see the EIA glossary).
Industrial sector
An end-use sector that consists of all facilities and equipment used for producing, processing, or assembling goods. The industrial sector is comprised of: manufacturing; agriculture, forestry, and fisheries; mining; and construction. Establishments in this sector range from steel mills, to small farms, to companies assembling electronic components. 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. (see the EIA glossary).
Residential Buildings sector
An end-use 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. (see the EIA glossary).
Commercial Buildings sector
An end-use 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. 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. (see the EIA glossary).
Electricity sector
An energy consuming sector that generates electricity. Data are organized to separate electricity-only generators from combined heat and power (CHP) generators. The electric-only generators provide power to residences, commercial establishments, and industry within the same harmonized grid through transmission and distribution lines. CHP generators may sell power to the wholesale market but they also provide heat (usually in the form of steam) to themselves or to other customers. CHP generators are further classified as electric-only, commercial, and industrial, depending on who purchases the power.
Subsectors
A subsector reflects the differentiated level of economic activity within a given sector. There are several various levels of subsector detail. Examples of subsectors used in the national system of indicators on this website are:
  • In the transportation sector, the subsectors are first passenger versus freight, but then each of these can be further disaggregated into modes of travel — air, rail, water, bus, automobile, truck, and light-duty vehicles.

  • For the industrial sector, the first level of subsector division is between manufacturing and non-manufacturing (agriculture, forestry, fisheries, mining, and construction). Manufacturing is further disaggregated into major industry groups and then into industries.

  • The residential sector is disaggregated into single family detached buildings, multi-family dwellings, and apartments.

  • The commercial building sector is disaggregated into building types (warehouses, schools, office buildings, retail stores, etc.).

  • The electricity sector is divided into electric-only producers and producers of combined heat and power (CHP). CHP producers are further divided into electric-only, commercial, and industrial producers.
Output
(also referred to as Activity). The major activity that drives economic production for the economy or its sectors and subsectors. At the level of the aggregate economy output is measured by GDP. The output measures for sectors varies for each sector, The output measures for each of the sectors used for the national system of indicators on this website are as follows:
  • The transportation sector uses passenger-miles and freight ton-miles
  • The Industry sector uses the value of shipments (i.e., sales)
  • The residential sector uses households
  • The commercial building sector uses square-feet of floor space as the output measure
  • The electricity sector uses kilowatt hours of electricity produced
These sector output measures are all linked to GDP so that they can be weighted by energy use and aggregated to an economy-wide total.
Passenger-miles travelled
The total distance traveled by all passengers. It is calculated as the product of the occupancy rate in vehicles and the vehicle miles traveled (see the EIA Energy Efficiency Glossary).
Ton-mile
The product of the distance freight is hauled, measured in miles, and the weight of the cargo being hauled, measured in tons. Thus, moving one ton of freight one mile generates one ton mile (see the EIA Energy Efficiency Glossary).
Other explanatory factors
Other explanatory factors are changes that affect the energy intensity of a sector or subsector that does not reflect changes in the efficiency with which energy is used. It is useful to differentiate these factors into structural changes, behavioral changes and weather, although these distinctions are not always clear cut.
Structural change is further defined below; behavioral changes are changes due to changes in consumer preferences that are reflected in choices that effect energy use, but are not directly tied to energy efficiency changes. A third category of factors are other factors over which we have no control; clearly weather dominates this third category, but there may be others.
Structural change
As it affects energy efficiency, structural change is a change in "other explanatory factors" that affects the energy intensity that is unrelated to the efficiency with which energy is used. For example, a change in product or industry mix in the industrial sector could affect energy intensity but a shift in industrial output is unrelated to actual energy efficiency improvements (e.g., a decline in steel production, or an increase in the output of the electronics industry relative to the growth of other industries). A second example of a structural factor is population migration. Migration of population from colder regions to warmer regions would alter the energy intensity of the residential sector, but would not, of itself, change the efficiency of energy use in the residential sector. Another example of structural change is the long-term trend in business activity in the U.S. from goods producing industries to service producing industries.
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Content Last Updated: 09/17/2012