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Energy Intensity of different economies The graph shows the amount of energy it takes to produce a US $ of GNP for selected countries. GNP is based on 2004 purchasing power parity and 2000 dollars adjusted for inflation. Source: Energy Information Administration

Energy intensity is a measure of the energy efficiency of a nation's economy. It is calculated as units of energy per unit of GDP.

• High energy intensities indicate a high price or cost of converting energy into GDP.
• Low energy intensity indicates a lower price or cost of converting energy into GDP.

Many factors influence an economy's overall energy intensity. It may reflect requirements for general standards of living and weather conditions in an economy. It is not untypical for particularly cold or hot climates to require greater energy consumption in homes and workplaces for heating (furnaces, or electric heaters) or cooling (air conditioning, fans, refrigeration). A country with an advanced standard of living is more likely to have a wider prevalence of such consumer goods and thereby be impacted in its energy intensity than one with a lower standard of living.

Energy efficiency of appliances and buildings (through use of building materials and methods, such as insulation), fuel economy of vehicles, vehicular distances travelled (frequency of travel or larger geographical distances), better methods and patterns of transportation, capacities and utility of mass transit, energy rationing or conservation efforts, 'off-grid' energy sources, and stochastic economic shocks such as disruptions of energy due to natural disasters, wars, massive power outages or unexpected new sources or efficient uses of energy may all impact overall energy intensity of a nation.

Thus, a nation with mild and temperate weather, demographic patterns of work places close to home, and uses fuel efficient vehicles, supports carpools, mass transportation or walks or rides bicycles, will have a far lower energy intensity than a nation with extreme weather conditions requiring heating and cooling, long commutes, and extensive use of generally poor fuel economy vehicles.

• U.S. energy consumption in 2004 was estimated at 99.74 quadrillion Btus (1.05 × 10¹¹ GJ) (referred to as 'quads') from all sources (US DoE). Total GDP was estimated at $11.75 trillion in 2004 and US GDP per capita was estimated at roughly $40 100 in 2004 (CIA Factbook). Using a population of 290,809,777 (as per US Census Bureau). This would produce an Energy Intensity of 8 553 Btus (9 MJ )consumed to produce a single dollar of GDP.

Various nations have significantly higher or lower energy intensities.

• Bangladesh, with a population of 144 million and a GDP of $275.5 billion therefore has a GDP per capita of approximately $2000. Its annual energy consumption was only 0.61 quads, making its Energy Intensity a mere 2113 kJ (a quarter of the US value.) Low standards of living and economic performance primarily accounts for such a meager number.

• Russia, with a population of 143 million and a GDP of $1.408 trillion therefore has a GDP per capita of approximately $9 800. Its annual energy consumption was 29.6 quads, for an Energy Intensity of 20 676 kJ(more than twice the US value), largely due to harsh climatic conditions in most of Eastern Russia and the country's vast territorial space.

Of course, these numbers were produced with a mix of 2003 and 2004 figures, many of which are estimates. Actual mathematical models should use precise data of appropriate matching periods of study.

GDP per capita vs. 'Economic Energy Efficiency' plotted for the top 40 national economies.

An inverse way of looking at the issue would be an 'economic energy efficiency,' or economic rate of return on its consumption of energy: how many economic units of GDP are produced by the consumption of units of energy.

• Referring to the above examples, 1 million Btus consumed with an Energy Intensity of 8,553 produced $116.92 of GDP for the US. Whereas, each million Btus of energy consumed in Bangladesh with an Energy Intensity of 2,113 produced $473 of GDP. Over four times the effective US rate. Russia, on the other hand, produces only $48.37 GDP per 1 million Btu based on an energy intensity of 20,676. Thus, Bangladesh could be perceived as having nearly ten times the economic energy efficiency of Russia.

It is not directly causal that a high GDP per capita must have lower economic energy efficiencies. See the accompanying chart for examples based on the top 40 national economies.

• Over-illumination
• World energy resources and consumption

• data up to 2003 at EIA [1]

Energy Intensity (UN Department of Economic and Social Affairs)