This section provides details about the methodology of the 2025 edition of the ETI. It is comprised of the following parts: –Index design, composition and calculation –Coverage and indicator selection criteria –Comparability and updates in the 2025 ETI Index design, composition and calculation The ETI framework is structured to ensure: –Balanced perspectives on current performance and future readiness –Diversity in energy transition pathways, accounting for context-specific challenges –Alignment with international frameworks and energy goals –Comparability across time, with data going back to 2015 –Contextualized, data-driven analysis for meaningful insights –Forward-looking orientation, enabling actionable outcomesThe ETI score is calculated as a weighted average of two sub-indices. Each sub-index is the arithmetic average of its component dimensions, which in turn are based on the index’s 43 underlying indicators (Figure 12). The ETI 2025 results reflect the latest available data at the time of collection. The ETI score uses a 0-100 scale, where 100 represents the best possible value and 0 the worst. To allow comparability and aggregation, each indicator is normalized to the 0-100 scale using a minimum-maximum formula. The sample minimum and sample maximum are the lowest and highest values for countries covered by the ETI. For those indicators for which a higher raw value indicates a worse outcome (e.g. wholesale gas prices), the study relies on a normalization formula that, in addition to converting the series to a 0-100 scale, reverses it, so that 0 and 100 still correspond to the worst and best, respectively. In many cases, however, adjustments are made to the sample minimum and maximum to account for issues such as outliers, with winsorization being the most common technique. Appendices A1.1 ETI methodology 100 x ( (country value – sample minimum sample maximum – sample minimum Fostering Effective Energy Transition 2025 51