The Energy Returned on Energy Invested (EROEI) concept is very frequently used in energy studies. In fact, many readers seem to think, “Of course, EROEI is what we should be looking at when comparing different types of energy. What else is important?” Unfortunately, the closer to the discussions of researchers a person gets, the more problems a person discovers. People who work with EROEI regularly say, “EROEI is a tool, but it is a blunt tool. An EROEI of 100 is good compared to an EROEI of 10. For small differences, it is not so clear.”
Because of the idiosyncrasies of how EROEI works, different researchers using EROEI analyses come to very different conclusions. This issue has recently come up in two different solar PV analyses. One author used EROEI analysis to justify scaling up of solar PV. Another author published an article in Nature Communications that claims, “A break-even between the cumulative disadvantages and benefits of photovoltaics, for both energy use and greenhouse gas emissions, occurs between 1997 and 2018, depending on photovoltaic performance and model uncertainties.”
Other EROEI researchers with whom I correspond don’t agree with these conclusions. They recognize that in complex situations, EROEI analyses cannot cover everything. Somehow, the user needs to be informed enough to realize that these omissions result in biases. Researchers need to work around these biases when coming to conclusions. They themselves do it (or try to); why can’t everyone else?
The underlying problem with EROEI calculations is that EROEI is based on a very simple model. The model works passably well in simple situations, but it was not designed to handle the complexities of intermittent renewables, such as wind and solar PV. Indirect costs, and costs that are hard to measure, tend to get left out. The result is a serious bias that tends to make the EROEIs of solar PV (as well as other intermittent energy sources, such as wind) appear far more favorable than they would be, if a level playing field were used. In fact, published EROEIs for solar PV (and wind) might be called misleading. This issue also exists for other similar calculations, such as Life Cycle Analyses and Energy Payback Periods.
