“The EROEI of Photo-Voltaics can be whatever you like these days” a friend of mine said once after attending a bio-physical economics conference. It epitomises a growing problem in this field, while the broad concept of net energy or Energy Return on Energy Invested (EROEI) is broadly accepted there is no unified methodology for its calculation. Different researchers apply different methods producing markedly different results. Photo-Voltaics (PV) is an energy source where this problem has been more acute. Equipment and installation prices collapsed four or five fold since 2010, but published EROEI studies have not converged; in fact it appears they dispersed even further. Fortunately, another friend, Rembrandt Koppelaar, has recently finished a study assessing these assorted EROEI estimates, entitled Solar-PV energy payback and net energy: Meta-assessment of study quality, reproducibility, and results harmonization . As it turns out, low EROEI figures are largely an artefact of outdated data […]