🔗 Share this article

Plug-in hybrid electric vehicles release nearly five times greater planet-heating pollution than official figures show, according to a recent analysis.

Growing Gap Between Lab and Real-World CO2 Output

Data shows that PHEVs release just one-fifth less CO₂ than traditional petrol and diesel vehicles, based on research carried out by a non-profit group. That differs significantly with laboratory estimates, which suggested a three-quarters reduction in emissions.

Analysts studied information from onboard energy use meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” stated a lead analyst involved in the report. “This discrepancy is growing and poses a serious problem. Consequently, PHEVs emit nearly as much as petrol cars.”

Primary Factors Behind the Emissions Gap

Researchers attributed most of the gap to overestimates of the “electric driving share” – the percentage of kilometers travelled in electric power compared to overall distance. The team determined that only a quarter of travel was completed in electric mode, whereas official assumptions assumed over four-fifths.

Additionally, when operating in EV mode, pollution amounts were significantly higher than lab estimates. That happened because EV motors were not strong sufficient to function independently, leading to engines using fossil fuels for almost a third of the travel covered in EV mode.

Regulatory and Financial Implications

According to calculations, the underestimation of PHEV emissions enabled several large automaker groups to escape over €5bn in fines between 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs could pay approximately €500 extra per year in running costs than is estimated under lab tests.

“The strong statements that manufacturers often promote about their PHEV cars are clearly way off the truth,” stated a automotive analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been drawn back into policy debates as automakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on new internal combustion cars in 2035 has faced intense pressure from the car sector and resistance from member states with large car manufacturing.

Some high-level politicians have proposed plug-in hybrids as a potential “compromise” solution to include in the legislation.

One independent energy policy expert, who was unaffiliated with the research, described the report a “very useful contribution” after a long period in which parts of the car industry argued there was too little information to properly evaluate real-world emissions.

“The results show, without question, that the difference between official and real-world PHEV energy use and CO₂ emissions is significantly larger than for gasoline or diesel cars,” the expert stated. “All policy adjustments regarding PHEVs should be made with extreme care and in the light of this evidence.”