Annual update cycle
DEFRA publishes updated greenhouse gas conversion factors every June, and the 2025 release brought several notable changes. These factors are the backbone of UK carbon reporting — used by thousands of organisations to convert activity data (kWh of gas, litres of diesel, km of flights) into CO₂ equivalent figures. Using the correct year's factors for your reporting period isn't just best practice, it's a requirement for SECR compliance and most voluntary frameworks.
Key changes in the 2025 factors
The most significant update was to the UK electricity grid factor, which dropped by 12% year-on-year reflecting the continued growth of renewable generation capacity. This means organisations reporting Scope 2 emissions will see a decrease even without changing their electricity consumption — an important nuance to communicate to stakeholders. Conversely, several freight transport factors increased due to updated modelling of vehicle efficiency degradation and supply chain complexity. Waste factors were also revised, with landfill factors increasing to reflect updated methane capture assumptions.
Impact on your reporting
If you're using 2024 factors for a 2025 reporting year, your Scope 2 figures will be overstated and your transport figures may be understated. For organisations tracking year-on-year trends, switching factors mid-series can distort your trajectory. Best practice is to recalculate your base year using the current year's methodology (but not necessarily the current year's factors) and clearly disclose which factor set you're using in your report.