Plug-in hybrids emit six times, on average, what official tests claim - new EU data

Carbon dioxide emissions from plug-in hybrid (PHEV) cars are six times higher, on average, than official tests suggest, according to new 2024 data published by the EU last week. The gap between PHEVs’ real-world CO₂ pollution and lab-based test results has actually widened every year since real world emission measurements started in 2021. The EU must reject efforts by carmakers to weaken rules designed to close the gap between official and real-world emissions and stop plug-in hybrids from falsely counting toward climate targets, T&E said.

PHEVs pair an electric battery with a petrol or diesel engine and currently account for 9.8% of EU car sales [1]. Last year, the European Commission made a major concession to carmakers by proposing to allow PHEV sales beyond 2035. Now, through their industry group ACEA, carmakers are pushing to cancel a planned 2027 regulatory update that would tighten the gap between real-world and official emissions.

However, latest data for cars registered in 2024 from the European Environment Agency (EEA) shows the gap is widening, not closing. Real-world PHEV emissions averaged 145g of CO₂ per km, compared to just 24g per km in official tests. In the data that the EEA released last year and analysed by T&E [2], real-world emissions of PHEVs registered in 2023 reached 138 g/km against test results of just 28 g/km —five times more emissions (+386%), compared to six times now (+500%).

The real world emissions of PHEV has increased 5% in just one year (between 2023 and 2024), despite the official emissions reducing by 15% (from 28 to 24 gCO₂/km) and carmakers claiming that the performance of PHEVs has improved since 2023.

With real world emissions at 145 g/km, PHEVs only emit 14% less than conventional combustion cars (169 g/km). The previous year, the gap between PHEVs and combustion cars was 17% on average - highlighting that PHEV emissions are increasingly similar to conventional combustion car emissions.

The real-world data was gathered from fuel monitors on 220,000 plug-in hybrid vehicles. It differs hugely from the laboratory tests where vehicles follow a standardized protocol, not representative of what can be considered to be normal driving. The EU has set to update ‘utility factors’ in 2025 and 2027 to correct CO₂ ratings and gradually tighten the gap, ensuring that PHEV design and performance are improved and that carmakers are not rewarded on paper for cars that pollute almost as much as combustion cars.

Lucien Mathieu, cars director at T&E, said: “Plug-in hybrids are one of the auto industry’s greatest greenwashing stunts - marketed as a green solution, yet delivering a heavy environmental toll in practice. They are also a major rip-off for consumers, who end up paying far more for fuel than expected. Carmakers are demanding that the EU turn a blind eye so it can delay investing in fully electric cars. Utility factors were designed to make official emission match with real-world; they are evidence-based policy making. If Europe wants to keep a chance to compete with China in the global EV race, it must resist any attempt to weaken the utility factors. ”

Negotiations on the revision of the car CO₂ standards are taking place now. The EU Council is expected to hold a debate on this on October 12, while a vote in the EU Parliament is due in November.

NOTES FOR EDITORS

[1] Data for H1 2026 from ACEA.

[2] T&E analysis of the real world performance of PHEVs registered in 2024, published in October 2025.