How the Measurement of Primary Energy Has Changed: From 'Substitution' to 'Physical Energy Content'

• The Energy Institute has transitioned its primary energy measurement methodology from the 'substitution method' to the 'physical energy content' method.
• This change is strictly an accounting adjustment; the physical reality of the global energy system remains unchanged.
• The shift primarily impacts how renewable energy sources like solar, wind, and hydropower are reported in historical data.

Methodology Changes

• Substitution Method (Previous): Inflated non-fossil energy figures by roughly 2.5x, using a hypothetical fossil fuel efficiency factor (approx. 38%–41%) to suggest what fuel would have been required if those sources were fossil-based.
• Physical Energy Content Method (Current): Measures the total energy supply directly. Solar PV, wind, and hydropower output are recorded at their actual generation value (e.g., 100 TWh of generation equals 100 TWh of primary energy).

Impact on Energy Data

• Solar, Wind, and Hydropower: Reported primary energy values decrease significantly as they are no longer inflated by the fossil fuel equivalent factor.
• Nuclear Energy: Values increase slightly because the calculation now uses the specific thermal efficiency of nuclear power (approx. 33%), which is lower than the previous substitution factor.
• Fossil Fuels: Continue to be measured by their raw calorific value; however, their share in the total energy mix will appear larger compared to the previous method due to the decrease in reported renewable energy volumes.
• Consistency: The new methodology has been applied to historical data series to ensure consistency across decades.