Misleading plug-in hybrid emissions figures risk cheating consumers, T&E warns

The gap between plug-in hybrids’ official CO₂ figures and their real-world emissions is widening. PHEV models registered in 2024 emitted around six times their official CO₂ figures on the road, up from a five-fold difference in 2023, according to a new T&E report. This gap adds €680 in extra annual fuel expenses for the average driver of a PHEV sold in 2024.

The analysis of European Environment Agency data finds PHEV real-world emissions just 14% lower than those of conventional combustion and hybrid cars, despite official test figures suggesting an 83% reduction. Even when the battery is powering the vehicle, the combustion engine operates for roughly a third of kilometres driven.

The EU is addressing the real-world emissions discrepancy by correcting the “utility factor”, which sets the share of driving powered by electricity when calculating official PHEV emissions. T&E finds that the first correction in 2025/6 has already encouraged manufacturers to fit larger batteries and extend electric range. According to the report, longer electric range offset three-quarters of the utility factor-related rise in official CO₂ emissions for upgraded models.

The analysis also finds that further technology and design progress could keep emissions below 50 grams of CO₂ per kilometer (gCO₂/km) [1] once the EU PHEV emission rules have been further corrected. With the next correction of the PHEV accounting rules due to start in November 2026, T&E urges governments to keep it in place to account for the real emissions of PHEVs. The warning comes as Germany pushes to freeze upcoming PHEV utility factor correction as part of France-German negotiations on a broader automotive package deal. 

Lucien Mathieu, cars director at T&E, says: “Rolling back the next correction means deliberately manipulating European car emissions math. If Germany gets its way, carmakers will keep overstating how much PHEVs drive electric, leaving consumers with higher fuel bills and stretching the EU’s oil dependency. The utility factor correction is doing more than fixing misleading emissions figures. It is pushing carmakers to improve the range of PHEVs.”

T&E analysed 20 top selling models, representing 51% of the 2025 sales market. The VW Group introduced the most impactful upgrades in 2025 as a consequence of the utility factor correction. Improvements across five VW models offset 90% of the increase in official emissions associated with the correction. For example, VW’s Tiguan electric range more than doubled, from 55 km to 119 km, keeping official emissions at 36 gCO₂/km compared with 32 gCO₂/km before the correction, thus helping drivers save fuel by running longer on the electric mode.

Manufacturers could further improve their vehicles under the next utility factor correction by greater electric range or efficiency in combustion mode, improved aerodynamics, lighter materials and better energy recovery.

Freezing the rules at the 2025–2026 level would continue to underestimate real-world PHEV emissions by 56% and significantly reduce the number of BEVs carmakers need to sell to comply with the 2030 target, according to T&E.

Mathieu says: “A decade after Dieselgate, it is outrageous that Europe is once again debating whether to keep using misleading emissions to sell cars. In ongoing negotiations on cars CO₂, the European Parliament and Council have a clear choice, protect drivers’ wallets or allow carmakers to continue lying to consumers. Drivers deserve the truth, not another fix to protect carmakers’ profits while leaving drivers hundreds of euros out of pocket.”

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Note to editors:

[1] Under both the EU CO₂ performance standards for new passenger cars and light commercial vehicles and the Regulation on Clean Corporate Vehicles, a Zero- and Low-Emission Vehicle (ZLEV) is defined as a car or van that emits between 0 and 50 g CO₂/km. The threshold is also used in national fiscal rules from 12 out of 27 EU Member States.