Most energy decarbonization scenarios prioritize cost-minimizing technical strategies, overlooking the environmental and social implications beyond greenhouse gas (GHG) emission reduction. This neglects crucial aspects of sustainable transformation, such as resource extraction impacts and energy import consequences. Growing attention towards broader sustainability dimensions beyond climate change mitigation highlights demand-side solutions, particularly sufficiency strategies, which enhance the likelihood of meeting climate goals and align with Sustainable Development Goals. However, most techno-economic optimization approaches ignore demand-side, especially sufficiency, strategies. Energy sufficiency focuses on reducing the absolute consumption and production of end-use products and services through societal practice changes, supported by appropriate infrastructure and frameworks. This approach aims to stay within planetary boundaries while ensuring decent living standards for all. Studies suggest a significant potential for global final energy consumption reduction (60% by 2050 by Millward-Hopkins et al., and 40% by Grubler et al.) through a combination of efficiency and sufficiency measures to meet climate targets. This paper presents the Collaborative Low Energy Vision for the European Region (CLEVER) scenario, a detailed European-level model emphasizing sufficiency and intra-European energy exchange, aiming for substantial energy import reduction, phasing out nuclear power, and avoiding carbon capture and storage (CCS) technologies by 2050, while considering social and environmental sustainability.

Existing literature demonstrates a significant potential for energy demand reduction in developed nations. Several studies, including the Low Energy Demand (LED) scenario for the Global North, the Transform scenario for the UK, a 2050 energy scenario for France, and Germany's RESCUE GreenSupreme scenario, highlight a potential final energy reduction of approximately 50-55%. A consistent finding across these scenarios is that prioritizing energy demand reduction eliminates the need for CCS technologies to reach net-zero emissions. Research further suggests that lower final energy demand, achieved through sufficiency, reduces energy system transition costs. This is due to the smaller energy systems requiring less renewable infrastructure and eliminating the need for expensive carbon capture technologies. The CLEVER scenario builds on this research by focusing on a collaborative, European-level model, exploring the potential of sufficiency and intra-European energy exchange to reduce reliance on external energy sources and high-risk technologies.

The CLEVER scenario uses a bottom-up, collaborative modeling approach involving 26 organizations from 20 European countries. The process involved several steps: 1. Development of bottom-up national trajectories, drawing upon existing national models or data where available; 2. Comparison of national trajectory ambition levels, guided by references and EU targets, to ensure a harmonized European scenario; 3. Data harmonization and convergence of sufficiency indicators until 2050; 4. Synthesis and iteration to achieve European sustainability targets. National trajectories were developed by active partners, while normalized (conservative) trajectories were developed and reviewed by national experts for countries without active partners. Target level corridors for key indicators (e.g., heated living space, passenger-kilometers) were defined using literature data, considering minimum levels based on decent living standards and maximum levels based on 1.5°C compatible service levels. Sufficiency indicators encompassed dimensional, service-related, and organizational aspects of energy consumption. Exceptions to target corridor levels were made for justified national specificities. The model includes detailed national energy and emissions pathways for 30 European countries, covering energy service demands, carriers, and production data for each end-use sector. For the industry sector, a top-down, centralized approach was adopted, focusing on sufficiency (scaling down material demand), circularity (optimizing product lifecycles), and efficiency (reducing energy intensity of production). The historic rate of production over consumption of materials was maintained. For the Agriculture, Forestry, and Other Land Use and Bioenergy (AFOLUB) sector, initial top-down modelling was refined with national partner input, focusing on emission mitigation, fossil fuel substitution, and carbon sequestration through sustainable bioeconomy practices (diet shift, agroecology) and biomass prioritization. The harmonization of national trajectories involved data collection, corridor definition based on literature, expert input, and EU policies, and iterative adaptation of national trajectories to comply with corridors and EU targets. The European synthesis module ensured consistency with EU targets and energy carrier balance. The supply-demand matching process prioritized sectors with limited decarbonization options and smaller low-carbon potentials, considering technological readiness levels (TRL) and sustainability issues. Territorial-based emission accounting and a maintained historic production-consumption rate were used. The model simplifies assumptions regarding system adequacy and flexibility; a detailed hourly dispatch model was not used, but a conservative value for flexible power generation ensures flexibility requirements. Furthermore, the electrical grid is not explicitly modeled, and congestion is disregarded. Investment requirements for new generation capacities and flexibility resources are also not quantified.

The CLEVER scenario projects significant GHG emission reductions: approximately 50% by 2030, 90% by 2040, reaching net-zero emissions by 2046 without nuclear power or CCS. Remaining emissions are offset by natural carbon sinks. The scenario achieves a 50.3% reduction in total final energy consumption (from 13,250 TWh to 6590 TWh) from 2019 to 2050, with per capita reductions ranging from 27% to 72% across EU30 countries. At least 40% of this reduction is attributed to sufficiency measures. Sufficiency plays a key role in reducing final energy consumption across various sectors. In the industrial sector, sufficiency in other sectors (buildings, transport, food) drives reductions in industrial demand for materials like steel and cement. The substantial reduction in final energy demand has significant implications for the energy supply transformation. It leads to a smaller energy system, minimizing the need for renewable energy infrastructure, reducing electricity grid expansion, and almost eliminating dependence on energy imports. Renewable energy sources, primarily solar PV, onshore and offshore wind, increase significantly. Bioenergy contribution is carefully managed to minimize land-use change impacts. Total extra-EU imports are reduced tenfold. The study highlights the importance of intra-European energy exchange through hydrogen and power transmission, fostering energy security and resilience. The analysis shows that the energy system in 2050 will be significantly smaller than in 2019, highlighting the effectiveness of a sufficiency-led approach. Figure 2 shows that Western European countries, currently high energy consumers, are expected to contribute the most towards demand reduction.

The CLEVER scenario aligns with other low-energy demand scenarios demonstrating substantial final energy reduction potential (around 50-55%). This consistency underscores the importance of demand-side strategies in achieving net-zero emissions without CCS. The scenario demonstrates that lower final energy demand, achieved through sufficiency, potentially reduces the overall cost of energy system transitions. This is due to reduced infrastructure needs, fewer residual emissions, and the elimination of expensive carbon capture technologies. The increased integration of domestic European energy systems via hydrogen and power exchange further reduces costs. While the CLEVER scenario doesn’t explicitly model costs and investments, it highlights the significant cost-saving potential associated with sufficiency-led pathways. While reducing national average energy consumption, the model acknowledges potential challenges related to intra-country inequalities. The scenario addresses this by setting sufficiency floors above recommended minimums to ensure even the lowest consumers maintain decent living standards. However, future work should investigate income inequality's impact on energy service access and its compatibility with decent living thresholds, ensuring fair intra-country distribution of sufficiency measures.

The CLEVER scenario demonstrates the critical role of sufficiency in achieving carbon neutrality and energy security in Europe by 2050. The significant reduction in final energy demand, driven primarily by sufficiency measures, leads to a smaller, more resilient, and less import-dependent energy system. The results highlight the need for integrating sufficiency policies into EU frameworks and scenario studies to achieve ambitious climate goals. Future research should focus on refining intra-country sufficiency distribution, detailed policy instrument modeling, and further exploring the interplay between sufficiency and other sustainability goals.

The CLEVER scenario simplifies some aspects of energy system modeling. System adequacy and flexibility are not explicitly modeled using an hourly dispatch model, although a conservative estimate of flexible power generation is included. The electrical grid isn't explicitly modeled, disregarding potential congestion issues. The investment costs for new generation capacities and flexibility resources are not quantified. The territorial-based emission accounting and the maintained historic rate of production over consumption limit the analysis's scope, necessitating a consumption-based accounting approach for a more holistic assessment.