Who will foot the bill? The opportunity cost of prioritising nuclear power over renewable energy for the case of Finland

In an effort to decarbonise their energy systems, several countries have declared intentions to triple their nuclear power capacity by 2050 at the United Nations Framework Convention on Climate Change Conference of the Parties 28. The expansion of nuclear power includes plans for so-called small modular reactors, intended for electricity generation as well as combined heat and power production. This study aims to demonstrate the cost differences between nuclear-based and renewables-based energy-industry systems using the Finnish energy system as a case study. Four nuclear power expansion scenarios are examined, imposing 13.2 GW of nuclear power capacity into Finland’s energy supply mix, with various capacities of small- and large-scale nuclear power plants alongside combined heat and power production from small-scale nuclear plants. These nuclear tripling scenarios are compared to a reference scenario that simulates a free cost optimisation with zero emissions target. The nuclear scenarios show 71-84% higher annualised system cost of 18.4-19.7 b€ compared to a renewables-based system costing 10.7 b€ in 2050. The reference scenario does not include the installation of new nuclear power capacities, indicating that new nuclear power plants are not part of a cost-optimal system. Additionally, the energy-industry system outlined in the reference scenario possesses fewer risks compared to nuclear tripling scenarios, particularly given that SMR technologies are not yet commercially available. The findings have important implications for energy justice, especially in terms of the significant opportunity cost presented by the nuclear decarbonisation pathway. • Tripling nuclear power is more expensive than optimised renewables in Finland • Tripling nuclear power costs over 71% more, equal to 2.3% of Finland's GDP • Tripling nuclear power exacerbates local social inequalities • Renewables meet energy demand more cost-effectively and avoid nuclear risks • Timely insights for policymakers quantifying the costs of nuclear power expansion