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PHEVs produce nearly five times greater global warming pollution than lab-reported figures show, according to a new analysis.

Widening Discrepancy In Lab and Actual Emissions

Data reveals that PHEVs emit just 19% lower CO₂ than traditional gas and diesel cars, based on analysis carried out by a non-profit organization. That differs significantly with lab tests, which suggested a 75% decrease in emissions.

Researchers studied information from onboard energy use monitors of 800,000 cars registered in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are decreasing,” said a senior researcher involved in the study. “That discrepancy is growing and poses a significant issue. Consequently, PHEVs emit almost as heavily as petrol cars.”

Key Factors Behind the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery power compared to overall distance. They found that just 27% of travel was done in EV mode, whereas lab assumptions suggested 84%.

Additionally, when operating in EV mode, emission levels were well above official projections. That happened because electric motors were not strong enough to function alone, leading to combustion motors burning gasoline for nearly a third of the travel covered in EV mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV CO2 output enabled several large automaker groups to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs could pay about €500 more per year in operating expenses than would be assumed under lab tests.

“The bold claims that automakers like to make about their PHEV cars are obviously way off the truth,” commented a automotive analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Pressure

Hybrid cars have recently been drawn again into policy debates as automakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on new combustion engine vehicles in 2035 has faced intense pressure from the car sector and resistance from member states with significant car industries.

Some high-level officials have proposed PHEVs as a possible “compromise” solution to introduce in the legislation.

One external energy policy specialist, who was unaffiliated with the research, described the analysis a “very useful addition” after a long period in which parts of the car sector argued there was insufficient data to accurately evaluate actual CO2 output.

“The results show, beyond any doubt, that the difference between official and actual PHEV energy use and CO₂ output is much, much larger than for petrol or conventional vehicles,” the expert stated. “Any regulatory adjustments regarding PHEVs should be made with extreme care and considering that data.”