A high EROI indicates cost-effectiveness or even profit for an energy system or technology while a low number indicates generating energy from that particular source is expensive. An EROI value of 7 is considered break-even[2] while some studies argue that an EROI value of 1 is the minimum requirement for a technology to be energetically sustainable.[3]
In its simplest form, the formula for EROI is described in Equation (2).[4]
EROI = Total Energy Output / Total Energy Input
Source: WEISSBACH ET AL; “COMPARISON WITH OTHER RESULTS”; ENERGY INTENSITIES, EROIS (ENERGY RETURNED ON INVESTED), AND ENERGY PAYBACK TIMES OF ELECTRICITY GENERATING POWER PLANTS
| 2010 | 2030 | 2050 | |
| Biomass with CCS | – | – | – |
| Biomass and waste | 11.4 | 6.3 | 5.9 |
| Ocean | 5.5 | 2.4 | 2.9 |
| Geothermal | 5.4 | 5.2 | 5.1 |
| Solar CSP | 21.6 | 8.9 | 9.1 |
| Solar PV | 9.3 | 7.4 | 7.2 |
| Wind offshore | 9.4 | 11.0 | 10.5 |
| Wind onshore | 9.5 | 9.3 | 8.1 |
| Hydro | 13.2 | 11.9 | 11.9 |
| Nuclear | 10.5 | 7.3 | 7.0 |
| Gas with CCS | – | – | 7.5 |
| Coal with CCS | – | – | 6.2 |
| Oil | 8.4 | 9.8 | 9.9 |
| Gas | 13.9 | 15.0 | 14.9 |
| Coal | 12.9 | 11.5 | 11.5 |
| TOTAL | 12.2 | 10.9 | 10.7 |
EROI’s and share in electricity mix of energy technologies using the THEMIS model for business-as-usual scenario
Source: ADRIEN FABRE. “ESTIMATION OF CURRENT AND FUTURE EROI’S USING THEMIS.” EVOLUTION OF EROIS OF ELECTRICITY UNTIL 2050: ESTIMATION AND IMPLICATIONS ON PRICES
[1] Adrien Fabre, Evolution of EROIs of electricity until 2050: Estimation and implications on prices, 3. [2] Daniel Weissbach et al., Energy intensities, EROIs (energy returned on invested), and energy payback times of electricity generating power plants, 5. [3] Adrien Fabre, Evolution of EROIs of electricity until 2050: Estimation and implications on prices, 1. [4] Paul Brockway et al., Estimation of global final-stage energy-returnon- investment for fossil fuels with comparison to renewable energy sources, 1.]]>
In a report by the International Energy Agency on estimated generation costs of various technologies existing across the globe by 2025, the LCOE can be calculated using Equation (1) where t is the year of sale of production, the summation S is from the start of construction preparation to the end of dismantling, and r corresponds to the discount rate according to the cost of capital.
Source: INTERNATIONAL ENERGY AGENCY; “LCOE VALUES BY TECHNOLOGY AND COUNTRY”; PROJECTED COSTS OF GENERATING ELECTRICITY
[1] Ibrahim Dincer et al., Comprehensive Energy Systems, 288. [2] USAID and U.S. National Renewable Energy Laboratory, Exploring Renewable Energy Opportunities in select Southeast Asian Countries, 1. [3] IEA, Projected Costs of Generating Electricity, 75.]]>