The main convention used for energy data is to refer to the actual energy content of each energy source at each stage. In particular, this means that the amount of electricity generated by hydropower and by wind power is considered directly as primary energy production.
For nuclear power, the amount of heat supplied for the generation of electricity is the primary energy input. Given the average thermal efficiency of a nuclear power station, the amount of heat supplied is about three times the amount of electricity generated. The amount of electricity produced in a conventional thermal power station may also be as little as one third of the amount of fossil fuel inputs, correctly reflecting the efficiency of traditional power stations (CEC, 1988).
- Gross energy consumption corresponds to the total primary energy consumed, including quantities delivered to marine bunkers.
- Gross inland consumption (or Total Primary Energy Supply (TPES)) is indigenous primary production, plus imports, minus exports and international marine bunkers, and plus/minus stock changes of primary energy.
- Final energy consumption is the consumption of primary and derived energy by the end-use sectors: mainly industry, transport, and households and services/commerce. Final energy consumption is always lower than gross inland consumption since it does not include the energy losses in conversion and distribution. Where 'consumption' is referred to in this chapter, this is gross inland consumption, unless otherwise specified, since this is more representative of the actual energy consumed in an economy. Where energy use is subdivided by end use sector or by fuel type, these data relate to final energy consumption.
- Energy intensity is a statistical measure which relates energy consumption (eg, gross inland consumption) to the level of economic activity (eg, GDP). Thus trends in energy intensity reflect changes in the amount of energy needed to produce a unit of economic output. This indicator is dependent on the efficiency of using energy for the various energy services required (eg, light, heat, power) and the structure of economic and social activities (eg, a high proportion of heavy industries consuming large amounts of fuel being used at comparably low efficiency, versus a service-oriented society).
- Energy efficiency is a measure of the overall efficiency of providing energy services, ie, the efficiency with which energy is produced from primary resources, transformed into useful forms, delivered to end users and consumers.
- Energy conservation is usually taken to refer just to the energy saving on the demand side.