EROI (Energy Return on Investment)
The ratio of usable energy delivered by an energy source over its lifetime to the energy invested to obtain and deliver it.
Energy return on investment (EROI or EROEI) measures how much energy a source returns for each unit of energy spent extracting, building, operating and decommissioning it. An EROI of 1 means a source only breaks even energetically; society needs sources well above 1 to fund all other activities.
Published values vary greatly with system boundaries (point of extraction versus point of use), whether electricity output is converted to primary energy equivalents, and whether storage is included. Indicative ranges from the literature:
- Conventional oil and gas at the wellhead: historically 30 to 100, declining to about 10 to 20 for many fields today (Hall et al. 2014).
- Coal at the mine mouth: about 20 to 80.
- Hydropower: 50 to over 100, owing to long lifetimes.
- Onshore wind: about 20 to 50; solar PV about 10 to 30, rising with efficiency gains and lower manufacturing energy.
- Nuclear: disputed, roughly 10 to 75 depending on enrichment method and boundaries.
Brockway et al. (2019, Nature Energy) showed that fossil fuels measured at the point of final energy have a much lower EROI, about 6, than at extraction, narrowing the gap with renewables. Weißbach et al. (2013) argued that storage-buffered renewables score lower. EROI complements energy payback time and lifecycle emissions analysis.
Related terms
All terms →- Energy payback time
The time an energy system must operate to generate as much energy as was used to manufacture, install and decommission it.
- Lifecycle emissions
Total greenhouse gas emissions of a product or power source across its full life, from raw material extraction and manufacturing through operation to decommissioning.
- Primary energy
Energy in its raw natural form before conversion, such as crude oil, coal, natural gas, uranium, biomass, and the electricity or heat from renewables.
- Final energy
Energy delivered to end users (households, industry, transport, services) in forms such as electricity, fuels and district heat, after conversion and transmission.
- Learning rate (Swanson's law)
The percentage cost reduction of a technology for every doubling of cumulative production; for solar modules, Swanson’s law puts it near 20%.
- Capacity factor
The ratio of the energy a power plant actually produces over a period to the energy it would produce running at full nameplate capacity for the whole period.