EROI Limitations

Two analysts study the same solar panel and publish EROI values of 3:1 and 20:1. Both are using legitimate methodology. The number is not wrong; the boundary is different.

EROI calculations depend entirely on which energy inputs the analyst chooses to count, and no standard methodology exists to resolve that choice. Unlike LCOE, which has a defined cost-accounting framework, EROI has no agreed boundary rule, making published figures across studies nearly impossible to compare directly.

The boundary problem works like this: do you count only the fuel burned at the extraction site, or also the energy to manufacture the drill? The steel to build the refinery? The roads to the wellhead? The decommissioning energy decades later? Each expansion of the system boundary lowers the reported EROI. Studies on the same source can legitimately differ by a factor of three to ten depending on where the analyst draws the line.

Why the same source gets different scores

A meta-assessment that reproduced and harmonized 29 published solar PV studies traced most of the disagreement to boundary choices, not to differences in the panels being studied. Harmonized to a common boundary, the scattered estimates converged toward roughly 9:1.

If two studies use different boundaries, what does comparing their EROI numbers actually tell you?

Very little. You are comparing the analyst's methodological choices more than the underlying energy physics. This is why policy documents that cite a single EROI figure as decisive evidence should be read with skepticism.

For investment decisions and technology comparison, LCOE is usually the more tractable metric because its cost-accounting boundary is standardized. EROI remains valuable for long-run questions about energy system sustainability, but only when the boundary assumptions are stated explicitly and held constant across the sources being compared.