Energy Return on Investment (EROI), also known as Energy Returned on Energy Invested (ERoEI), is a fundamental concept in energy economics. It measures the efficiency of energy production by comparing the usable energy obtained from a specific resource to the energy expended in acquiring that resource. The concept was popularized by Charles A. S. Hall, a professor of Systems Ecology and Biophysical Economics during 1980s. As of 2024, the approximate threshold for viability of the project requires EROI ratio of at least 3:1.
EROI for various renewable sources:
Hydroelectric Power:
Early studies by Gilliland et al. had estimated the EROI of small hydropower to be around 12. For medium sized plant of about 2.1MW, the EROI was found to be 33. Other studies such as by Murphy et al. has shown that the EROI of hydropower exceeds 100. Reservoir plants can have EROI of 205 while a run of river plant can have EROI of 267.
In general small hydro plants have a low EROI. Even though there may be some discrepancies in the study, the EROI for hydropower plants remains the highest among all the renewable sources.
Nuclear Plants:
Nuclear power systems exhibit an EROI that is one order of magnitude more effective than photovoltaics and wind power. EROI lies between 40 to 80. The studies however neglects the energy required to discard the byproducts. As such, this source has its own problems and risks and possibly will never be fully a clean energy.
Photovoltaic (PV) Modules:
EROIs for PV module technologies range from 8.7 to 34.2, with a 30-year system lifetime.
Wind Turbines:
EROI for wind turbines is approximately 4 to 20, varying based on the turbine size.
Conclusion
This way we can see that Hydropower plants has the largest EROI among various renewable sources and thus most sustainable energy source.
References
1. Atlason, R. S., and R. Unnthorsson. “Energy Return on Investment of Hydroelectric Power Generation Calculated Using a Standardised Methodology.” Renewable Energy 66 (June 1, 2014): 364–70. https://doi.org/10.1016/j.renene.2013.12.029.
