. "Life-Cycle Analysis: Net Energy Expenditure: A Method for Assessing the Environmental Impact of Technologies." Measures of Environmental Performance and Ecosystem Condition. Washington, DC: The National Academies Press, 1999.
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Representations of energy consumption, waste-stream discharges, and aesthetic preferences for four hypothetical technology systems.
specified and the rationale for their selection explained. Spelling out the specifications of an analysis makes it possible for others to repeat it, which lends validity and credibility to the results.
It is possible to apply sensitivity tests to an energy analysis by decreasing or increasing key energy terms and observing the effect on the results. (See, for example, Hocking, 1994b.) In this way, it is possible to identify the factors most important for decreasing the energy consumption of a technology. In the cup example, sensitivity tests demonstrated that the significant factors were the energy requirement for washing reusable cups and the fabrication energy for the disposable cups.
Although energy analysis can be used to compare widely differing technologies and is a useful tool for the quantitative determination of resource expenditure, it contributes little information on the relative emission characteristics of alternate technologies. The primary energy sources, whether coal-fired or gasfired boilers, or hydroelectric, will have different emission characteristics, but the energy assessment process itself does not give this information.