To reduce the European Union’s dependence on fossil fuels and diversify its energy supply before 2030, the REFORMERS project addresses the main problem of accelerating the transition to decentralised, integrated energy systems. The project advances the concept of Renewable Energy Valley (REVs): systems with high shares of renewable generation, storage technologies, and intelligent management algorithms. By enabling the synergistic operation of multiple technologies and energy carriers, REVs can become self-sufficient annually and provide a promising pathway towards a more resilient and sustainable European energy system. A key enabling technology is the digital twin, which supports the analysis, planning, optimisation, and control of renewable and multi-energy assets. Within REFORMERS, these solutions are not only developed and implemented in real-life settings but are also systematically scaled to support wider deployment across Europe. The methods used to achieve this are organised through a three-level living lab methodology designed for systematic scaling: 1. Level 1 (Controlled Testing): The Green Village is a small-scale living lab at Delft University of Technology campus, offering high data coverage and extensive asset control for testing and validation. It integrates residential and non-residential demand, PV, batteries, hydrogen storage, and electricity, heat, and hydrogen networks. Its district heating network supports thermal-flexibility experiments addressing grid congestion. 2. Level 2 (System-Level Demonstration): The Flagship REV in the Alkmaar–Heiloo region in the Netherlands comprises more than 500 businesses and over 5,000 households and integrates multiple energy hubs, short-term storage systems, and multi-energy carrier infrastructures, including heat and hydrogen networks. 3. Level 3 (Transnational Replication): In six Replication Valleys across Europe, common baseline assessments map energy systems, stakeholders, policy contexts and data availability; workshops then match relevant Flagship Valley solutions to local needs and define the required adaptations.This three-level setup (see Figure 1) enables a structured scaling pathway for energy system integration solutions, progressing from controlled experimentation to system-level demonstration and, ultimately, to transnational replication. The Green Village and the Flagship Valley are multi- vector energy systems that combine renewable generation, short-term battery storage, and hydrogen infrastructure, allowing solutions such as the digital twin to be validated in a controlled setting and applied in a more complex real-life context that shares similar technological building blocks. While The Green Village offers high observability and controllability at a small scale, the flagship valley captures the complexity of a larger integrated energy ecosystem. For example, we found that installing a 2 MWh battery addressed only part of the grid-congestion challenge; collective grid contracts, coordinated control and rules for allocating scarce capacity are also needed to enable multiple innovations and local businesses to operate. and the Replication Valleys demonstrate how comparable solutions can be adapted to diverse regional, climatic, and socio-economic contexts across Europe. The primary outcome of this progression is the generation of technical, operational, and organisational insights embedded in project-wide methods and implementation guidelines. In this way, the three-level scaling method combines scientific rigour with practical relevance, accelerating the translation of local innovation into transferable, widely deployable solutions for resilient and self-sufficient REVs across Europe.