The following definitions reflect those used by the International Energy Agency (IEA); definitions used by other organisations and publications may vary.


exploration and production


electric arc furnace


export credit agency


enhanced coalbed methane recovery


European Economic Area


Energy Efficiency Market Report (publication of the IEA)


Energy Efficiency Working Party (of the IEA)


Energy Frontier Research Center (United States)


enhanced gas recovery


Experts Group on Science for Energy (of the IEA), formerly known as the Ad Hoc Group on Science and Energy Technologies


Energy Information Administration (United States)


economies in transition: Russia, Former Soviet Union (FSU) and East & Central Europe (ECE)


electricity networks analysis, research and development


enhanced oil recovery


Environmental Protection Agency (United States)


engineering, procurement and construction


Emergency Response Exercise


Emergency Response Review


emission reduction units


electricity storage


energy service company


European Smart Meters Industry Group


ethyl tertiary butyl ether


energy technology collaboration


Energy Technologies Institute (United Kingdom)


Energy Technology Perspectives (IEA publication)


emissions trading scheme


European Union allowances


Energy-using product


Eurostat is the statistical office of the European Union


electric vehicle


external costs of energy (research project of the European Commission)

electric vehicle (EV)

a plug-in, battery electric vehicle. It is sometimes also termed ‘battery electric vehicle’. EVs do not have an internal combustion engine.

electricity generation

the total amount of electricity generated by power only or combined heat and power plants including generation required for own use. This is also referred to as gross generation.

electricity production

the total amount of electricity generated by a power plant. It includes own-use electricity, as well as transmission and distribution losses.

Emergency Response Exercises

main objective is to train relevant government officials and oil industry stakeholders in emergency procedures. IEA work in this area began with the development of Emergency Response Exercises for member countries in the wake of oil supply disruptions in the 1970s, which threatened the global economy.

emission quota

the portion or share of total allowable emissions assigned to a country or group of countries within a framework of maximum total emissions and mandatory allocations of resources or assessments (Intergovernmental Panel on Climate Change).

emission reduction units

each ERU represents 1 tonne of CO2 equivalent, generated under the Kyoto Protocol’s Joint Implementation provisions.

Energy Development Index

a composite measure of energy use in developing countries (developed by the IEA). Inputs are commercial energy consumption per capita, share of commercial energy in total final consumption (TFC), and share of population with access to electricity.

energy efficiency

something is more energy efficient if it delivers more services for the same energy input, or the same services for less energy input. For example, when a compact florescent light (CFL) bulb uses less energy than an incandescent bulb to produce the same amount of light, the CFL is considered to be more energy efficient. For more information

energy efficiency indicators

show policy makers where energy savings can be made.

energy intensity

a measure of total primary energy use per unit of gross domestic product.

energy poverty

a lack of access to modern energy services. These services are defined as household access to electricity and clean cooking facilities (e.g. fuels and stoves that do not cause air pollution in houses).

energy security

the uninterrupted availability of energy sources at an affordable price.

energy technology roadmap

each IEA Technology Roadmap focuses on a single technology and outlines a clear and systematic path for its deployment within a set time period. The roadmapping process involves detailed analysis and assessments of aspects such as research, development and deployment of the technology, the legal, regulatory and financial issues, and consumer acceptance issues.

enhanced oil recovery

also known as tertiary oil recovery, it follows primary recovery (oil produced by the natural pressure in the reservoir) and secondary recovery (using water injection). Various EOR technologies exist, such as steam injection, hydrocarbon injection, underground combustion and CO2 flooding.


is produced from fermenting any biomass high in carbohydrates. Today, ethanol is made from starches and sugars, but advanced generation technologies will allow it to be made from cellulose and hemicellulose, the fibrous material that makes up the bulk of most plant matter.

exchange-traded commodity

traded on an exchange which is controlled by rules and regulations, such as the New York Mercantile Exchange (NYMEX). A non-exchange traded commodity is traded between physical buyers and sellers outside of such an exchange.


exajoule (1 joule x 1018)