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EU moves to standardise transport emissions reporting as plug-in hybrid gap widens
9/6/2026
News
New EU rules introducing a standardised methodology for calculating transport emissions have entered into force. In other news, policymakers are stepping up efforts to address persistent gaps between official figures and real-world performance.
The CountEmissionsEU framework establishes a single approach for cars and trucks aligned with international standard EN ISO 14083:2023, creating a science-based system for measuring emissions across all transport modes. It aims to enable consistent, comparable reporting for both freight and passenger journeys. Previously different rules applied to passenger and commercial vehicles.
By enabling door-to-door emissions calculations, the framework is intended to support more accurate benchmarking of transport performance and inform procurement and operational decisions. It also aims to provide clearer data for consumers and public authorities.
The rules apply to companies that voluntarily disclose transport emissions, ensuring that reported figures are consistent and verifiable. Further work will refine the methodology, while the European Commission (EC) is set to roll out guidance and digital tools, particularly for small and mid-sized enterprises. Full application of the framework is expected by 2030.
The push for standardised reporting comes amid growing evidence that official emissions data does not reflect real-world performance, particularly for plug-in hybrid vehicles.
A study by the International Council on Clean Transportation (ICCT) finds that plug-in hybrid vehicles in Europe emit, on average, five times more CO2 in real-world conditions than official figures suggest. The gap between real-world and official values widened between 2021 and 2023, driven in part by overestimation of how often these vehicles operate in electric mode.
Plug-in hybrids accounted for around 9% of new car sales in Europe in 2025 and are often marketed as a lower-emissions alternative due to their ability to accept both mains power and road fuels, as well as their ability to switch between electric and combustion power. The findings add to evidence of their real-world emissions performance.
The EC revised the methodology used to calculate plug-in hybrid emissions in 2025, with further adjustments planned for 2027. At the same time, the EU’s CO2 emission reduction targets for cars are under review in the European Parliament, where an early draft proposes freezing future corrections to plug-in hybrid CO2 values.
‘Even with the 2025 correction, emissions on the road are not accurately estimated. And the worrying trend is that new models are not emitting less but more. Even if carmakers claim that consumers drive more kilometres in electric mode, the reality is something else,’ commented Peter Mock, Europe Director, ICCT.
The report finds that the gap between real-world and official emissions values grew from 265% in 2021 to 400% in 2023, on average across all manufacturers. Mercedes, the largest seller of plug-in hybrids between 2021 and 2023, recorded the widest gap, rising from 329% in 2021 to 614% in 2023, with a three-year average of 452%.
Plug-in hybrids show a larger divergence between real-world and official CO2 values than other powertrains. Based on ICCT estimates, the gap corresponds to approximately 100mn tonnes of CO2 from new registrations between 2021 and 2025, emissions that are not reflected in the EU’s CO2 reduction targets for carmakers.
The study covers around eight million vehicles, including petrol and diesel cars and their hybrid variants. Differences between real-world and official emissions are observed across all vehicle types, averaging around 20% for internal combustion vehicles, including full and mild hybrids, compared with around 400% for plug-in hybrids registered in 2023.
‘The gap of plug-in hybrids is shockingly high, but this should not distract from the fact that the gap of conventional vehicles, which still make up the majority of vehicle sales in the EU, is also considerably high at 20%. As a consequence, we didn’t see any notable reductions in the real-world CO2 emissions of vehicles with a combustion engine over the past years,’ said Jan Dornoff, ICCT Research Lead and co-author of the study.
Between 2018 and 2023, official average CO2 values for new cars fell by 28%, while real-world emissions declined by 15%. Battery electric hybrid vehicles accounted for most of the reduction. Real-world emissions from combustion engine cars decreased by around 1% over the same period.
