Plug-in Hybrid Cars Pollute Almost as Heavily as Gasoline Vehicles, Report Reveals

Plug-in hybrid electric vehicles release nearly five times greater global warming pollution than lab-reported data show, according to a new report.

Widening Discrepancy Between Lab and Real-World CO2 Output

Data shows that PHEVs emit only 19% lower CO₂ than traditional petrol and diesel cars, according to research carried out by a non-profit organization. That contrasts significantly with lab tests, which assumed a 75% reduction in emissions.

Analysts examined information from onboard energy use meters of 800,000 vehicles registered in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” said a senior analyst involved in the report. “This discrepancy is growing and poses a serious problem. Consequently, PHEVs emit nearly as much as petrol cars.”

Primary Reasons Driving the Discrepancy

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in electric mode compared to overall distance. The team determined that only 27% of travel was done in EV mode, while official estimates assumed 84%.

Even, when operating in electric mode, emission levels were significantly higher than official estimates. That happened because electric motors were not strong sufficient to operate alone, leading to combustion motors burning gasoline for almost a third of the travel completed in EV mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV emissions allowed four major carmaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 more per year in running expenses than would be assumed under lab conditions.

“The strong statements that manufacturers often promote about their PHEV cars are obviously far from the truth,” commented a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Discussion and Automotive Pressure

Hybrid cars have recently been drawn again into political debates as carmakers have lobbied the European Union to weaken CO₂ targets. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense pressure from the automotive industry and opposition from EU countries with significant car manufacturing.

Some senior officials have suggested PHEVs as a possible “flexibility” solution to introduce in the legislation.

An independent energy policy expert, who was unaffiliated with the study, described the analysis a “very useful addition” after years in which segments of the automotive industry claimed there was insufficient data to accurately assess real-world CO2 output.

“These findings show, without question, that the difference in official and real-world PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel vehicles,” they said. “All regulatory adjustments regarding PHEVs should be made with utmost caution and considering that data.”