EU Plug-in Hybrids Emit Six Times More CO2 Than Official Tests Claim
New data reveals a widening gap between laboratory ratings and real-world pollution, sparking a regulatory battle over 2027 emissions rules.
Plug-in hybrid electric vehicles (PHEVs) registered in the EU are polluting significantly more than their official ratings suggest, according to an analysis of new European data. The discrepancy suggests that these vehicles, often marketed as a bridge to full electrification, are failing to deliver their promised environmental benefits in practice.
Data analyzed by the advocacy group Transport & Environment (T&E) shows that 2024 PHEVs averaged 145 g/km of real-world CO2 emissions, while official laboratory ratings claimed just 24 g/km. This means real-world emissions are six times higher than the figures used for regulatory compliance. At 145 g/km, these hybrids are only 14% cleaner than conventional internal combustion engine vehicles, which average 169 g/km.
The Widening Gap
This disparity is not a new phenomenon, but it is accelerating. The emissions gap has widened every year since 2021, growing from 3.4 times the official rating in 2021 to 4.2 times in 2022, 4.9 times in 2023, and finally reaching the 6x multiplier in 2024.
The root of the problem lies in the "utility factor" (UF), the formula the EU uses to calculate official emissions. The UF assumes a specific percentage of driving is done in electric mode based on the car's battery range. However, onboard fuel monitors reveal that drivers charge their vehicles far less than the formula assumes. Consequently, the share of electric driving is actually declining even as manufacturers increase the theoretical electric range of the vehicles.
Industry Stakes
For automakers, the gap provides a critical financial cushion. By relying on optimistic laboratory ratings, manufacturers can meet fleet-wide CO2 targets on paper, allowing them to avoid billions of euros in potential fines. Lucien Mathieu, cars director at T&E, described plug-in hybrids as "one of the auto industry’s greatest greenwashing stunts," arguing they are marketed as green solutions while delivering a heavy environmental toll.
This financial incentive has led to a political clash in Brussels. Automotive industry groups, including the European Automobile Manufacturers' Association (ACEA), are currently lobbying the EU to cancel a scheduled regulatory update set for 2027. This update is designed to tighten utility factor calculations to better reflect actual driving habits.
Future Outlook
If the 2027 rule update is blocked, critics argue the EU will struggle to meet its broader climate targets. Furthermore, consumers may continue to pay a price premium for PHEVs under the impression they are significantly reducing their carbon footprint.
Attention now turns to the EU regulatory body to determine if the 2027 update will proceed. Until the calculations are aligned with real-world data, the PHEV will remain a contentious middle ground between the combustion engine and the battery-electric vehicle.