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Plug-in hybrid cars produce almost 5x greater planet-heating pollution than lab-reported data indicate, according to a new report.

Widening Gap In Lab and Actual CO2 Output

Statistics shows that PHEVs release only one-fifth less CO₂ than conventional gas and diesel vehicles, according to research conducted by a advocacy organization. This differs significantly with lab tests, which assumed a three-quarters reduction in emissions.

Researchers studied data from in-vehicle energy use meters of 800,000 cars sold in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are decreasing,” stated a lead analyst involved in the study. “This discrepancy is growing and creates a significant problem. Consequently, PHEVs emit almost as heavily as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Analysts attributed most of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in electric power compared to total mileage. They found that just a quarter of driving was done in electric mode, whereas official assumptions assumed over four-fifths.

Even, when running in electric mode, pollution amounts were significantly higher than lab projections. That happened because EV motors were not strong enough to function independently, resulting to combustion motors using gasoline for nearly a third of the distance covered in electric mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV emissions allowed four large automaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 extra per year in running expenses than would be estimated under lab tests.

“The strong claims that automakers often promote about their plug-in hybrid vehicles are clearly way off the mark,” commented a transport analyst. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Policy Discussion and Industry Lobbying

Hybrid vehicles have lately been drawn again into policy debates as automakers have pressed the EU to weaken CO₂ standards. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and opposition from EU countries with large car manufacturing.

Some high-level officials have proposed plug-in hybrids as a possible “flexibility” solution to include in the regulation.

One independent energy economics expert, who was not involved with the research, described the report a “very useful addition” after a long period in which segments of the car industry claimed there was insufficient information to properly assess real-world CO2 output.

“These findings demonstrate, without question, that the gap between lab and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or diesel cars,” they stated. “Any policy adjustments regarding PHEVs should be made with extreme care and considering this evidence.”