The gap between the performance figures quoted for plug-in hybrids and their actual usage continues to widen. The International Council on Clean Transportation (ICCT) analysed on-board fuel consumption data from around 920,000 vehicles registered in Europe between 2021 and 2023 and published the results on Thursday 3 September.

For cars registered in 2021, actual emissions averaged 3.5 times the official figures. This ratio has risen to 4.6 for the 2023 model year. By way of comparison, petrol and diesel cars, including mild hybrids, exceeded their type-approved figures by around 20%.

The paradox is that the electric range of plug-in models has increased. Yet the proportion of their journeys actually driven in electric mode has fallen. Between 2021 and 2023, their average actual emissions thus rose from 130 to 134 grams of CO₂ per kilometre, whilst the official figures fell from 37 to 29 grams.

Figures rarely seen on the road

The issue lies with the European type-approval formula, which links a longer electric range to increased use of this mode of travel. For 2022, it assumed an 80% share of electric driving, whereas a figure closer to 21% would have produced CO₂ figures more in line with reality, according to the ICCT.

This discrepancy works in the manufacturers’ favour when calculating their European emissions targets. “The low emissions figures attributed to plug-in hybrids are rarely achieved in real-world driving,” points out Jan Dornoff, a research fellow at the ICCT and author of the study.

The European Commission is due to revise this calculation method in 2027. Such a revision could make plug-in hybrids less attractive as a means for manufacturers to meet their CO₂ emission targets. These vehicles accounted for around 10% of new registrations in Europe between January and July 2026, compared with 22% for fully electric cars.