Abstract
For the purpose of measurement, energy sustainability is defined as ensuring that future
generations have energy resources that enable them to achieve a level of well-being at
least as good as that of the current generation. It is recognized that there are valid, more
comprehensive understandings of sustainability and that energy sustainability as defined
here is only meaningful when placed in a broader context. Still, measuring energy
sustainability is important to society because the rates of consumption of some fossil
resources are now substantial in relation to measures of ultimate resources, and because
conflicts between fossil energy use and environmental sustainability are intensifying.
Starting from the definition, an equation for energy sustainability is derived that reconciles
renewable fl ows and nonrenewable stocks, includes the transformation of energy
into energy services, incorporates technological change and, at least notionally, allows
for changes in the relationship between energy services and societal well-being. Energy
sustainability must be measured retrospectively as well as prospectively, and methods
for doing each are discussed. Connections to the sustainability of other resources are
also critical. The framework presented is merely a starting point; much remains to be
done to make it operational.