This section provides details about the methodology of the 2025 edition of the ETI. It is comprised of the following parts:

The ETI framework is structured to ensure:

The 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.

Figure 12: Methodology and indicators

The ETI 2025 assesses 118 countries. To be covered in the index, a country needs to have data for most of the index’s 43 indicators, including sufficient coverage for each dimension.

The following principles guide the selection of indicators:

1. Relevance: alignment of parameters with core aspects of the energy transition

2. Recency and comparability: use of the most recent and cross-country comparable data

3. Source quality and objectivity: reliance on credible, widely recognized and independent data sources

Comparability and updates in the ETI 2025: The ETI is a dynamic benchmark, with structural and indicator-level refinements applied each year to reflect evolving transition priorities and data availability. Moreover, data sources frequently revise data, changing historical results. As a result, direct comparisons of country rank and score between the ETI 2025 and previously published editions should be made with caution.

The following updates have been made to the 2025 ETI:

1. Indicator removals

The following indicators have been excluded from ETI 2025 due to data limitations, redundancy or methodological changes:

– Gas supply resilience

– International financial flows

– Regulatory Indicators for Sustainable Energy (RISE) Cook Score

– Rule of law

– Investment in renewable energy

2. Indicator name changes

To better reflect the parameters measured, the following indicators have been renamed:

– Carbon prices –> Net-effective carbon rates

– Quality of education –> Labour market competitiveness

– Public R&D spend –> R&D as share of GDP

3. New indicator addition

Economic freedom and investment in clean energy has been introduced as a new indicator under the regulation and political commitment and finance and investment sub-dimensions, respectively, to improve coverage of macroeconomic enablers in the energy transition.

Table 19: ETI model framework