<Tr> <Td> 9.5 </Td> <Td> Geothermal (without hot water heating) </Td> </Tr> <Tr> <Td> 32.4 </Td> <Td> Geothermal (with hot water heating) </Td> </Tr> <P> High per - capita energy use has been considered desirable as it is associated with a high standard of living based on energy - intensive machines . A society will generally exploit the highest available EROEI energy sources first, as these provide the most energy for the least effort . This is an example of David Ricardo's best - first principle . Then progressively lower quality ores or energy resources are used as the higher - quality ones are either exhausted or in use, for example, wind turbines positioned in the windiest areas . </P> <P> In regard to fossil fuels, when oil was originally discovered, it took on average one barrel of oil to find, extract, and process about 100 barrels of oil . The ratio, for discovery of fossil fuels in the United States, has declined steadily over the last century from about 1000: 1 in 1919 to only 5: 1 in the 2010s . </P>

How is energy return on investment (eroi) calculated for biomass and biofuels