Sustainability 2011 , 3
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about missing information that might remain unaccounted for. We define EROI in the normal way,
though by including all energy demands to the point of sale and release of the product for use by
others, has new meaning.
What becomes most clear is that understanding the true scale of energy needs of business is well
worth the added uncertainty of combining precise data with imprecise econometric measures. It
demonstrates that easy and imprecise measures are far more accurate than time consuming precise
measures when the latter are a small fraction of the total. As part of a whole system assessment
method, the further task is to consider how a better understanding of the business as a system helps
you understand its wider roles in the economic and natural environment, that affect business and public
values and decisions. We use that discussion for pointing to a sampling of other directions of study.
2.1. Measurement Strategies for System Energy Assessment
We use hybrid accounting to combine precise measures of energy use that are very incomplete with
rough statistical measures that are very comprehensive (Figure 3). When combining direct records of
energy use with statistically estimated energy uses the statistical estimate may need to be reduced to
having duplicate recorded and estimated amounts for the recorded energy use (Figure 5). We also
develop a strategy for the problem that every fuel use also costs money, and so has both embodied
energy content in the economic services that delivered the fuel, in addition to the physical energy
bound in the fuel itself. The money paid for fuels is paid to other people for the rights to it, and not for
the fuel itself. The fuels themselves come from nature, for “free” and are never paid for except in the
energy cost of extraction.
Figure 3. Estimating whole system energy use (outer circle) with overlapping direct
measures (islands) and proxy measures (inner circle). Direct records of technology energy
use (TE) need to be combined with estimated economic energy use (EE) at the world
average intensity ($E*EiW), and be corrected for overlap.