Revised 2 December 2023

Tom Murphy (2021) has provided indicative energy return on energy invested ratios for a range of fossil fuels and renewables in his 481-page book titled “Energy and Human Ambitions on a Finite Planet: Assessing and Adapting to Planetary Limits”. The ratios are indicative because net energy analysis estimates of EROI vary depending on which boundaries are applied. 

Table 1: Indicative Energy Returned on Energy Invested (Murphy 2021) 

Hydroelectric tops the ranking with an EROI ratio of 40:1 plus. There is limited remaining potential for large scale hydroelectric in most countries. Some countries are blessed with a high percentage of electricity production supported by hydro dams. New Zealand is one of them. 

Oil shale has a lower EROI ratio than renewables but, in terms of scale, has so far propped up increases in total net energy while net energy provided by legacy forms of fossil fuels has declined. 

We need to transition from fossil fuels to renewables, but what is clear is that the EROI of renewables will be less than that of fossil fuels in the 1970s when field oil peaked. What matters most is the scale of how much net energy can be produced from a combination of different renewables sources. A key question is whether renewable energy with a relatively low EROI ratio compared to fossil fuels in its heyday can scale up to replace and match the level of net energy currently provided by fossil fuels. Scaling up of net energy provided by renewables which have a lower EROI than fossil fuels in its heyday means using more renewables such as photovoltaic panels and wind turbines. That means more materials, the mining of which has a greater impact on the environment.