The energy production hierarchy: Which renewable technology should we install first?

To sustain modern society, the energy sector must maintain an Energy Return On Investment (EROI) ratio of ~15:1. With the imminent switch to renewable energy, this paper compares the EROI of photovoltaic, concentrated solar power, wind, hydropower, and geothermal energy for all European Union countries (EU27). The results show that only 8 countries currently have what could be described as an “optimum” renewable energy strategy – i.e., where the technology with the highest EROI and highest energy generation potential has the largest share of total renewable energy generation. More positively, 23 countries can produce their current electricity demand through renewable technologies whilst also maintaining the minimum EROI (~15:1). Notably, this entails that four countries are unable to do so – lending some support to the need for a collaborative approach in our energy transition and the necessity to “downscale” modern societies so that they can operate within their ecological ceiling.