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

Growing Discrepancy Between Lab and Real-World Emissions

Statistics reveals that PHEVs release only one-fifth lower CO₂ than traditional petrol and diesel cars, based on research conducted by a advocacy group. This contrasts significantly with lab tests, which assumed a three-quarters decrease in emissions.

Analysts studied data from onboard energy use meters of eight hundred thousand vehicles registered in Europe between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while official figures are decreasing,” said a lead analyst involved in the study. “This discrepancy is widening and creates a significant problem. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers linked the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers travelled in battery mode relative to overall distance. They found that only 27% of driving was done in EV mode, whereas lab assumptions suggested over four-fifths.

Even, when operating in electric mode, emission amounts were significantly higher than lab projections. That occurred because electric motors were not strong sufficient to function independently, resulting to engines using gasoline for nearly a third of the travel completed in electric mode.

Regulatory and Economic Implications

According to calculations, the underestimation of PHEV emissions enabled four major automaker groups to escape over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs could pay about €500 extra annually in operating costs than would be estimated under laboratory conditions.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are clearly far from the mark,” commented a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Pressure

Hybrid cars have recently been brought back into political debates as automakers have lobbied the EU to weaken CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced intense pressure from the automotive industry and opposition from member states with significant car manufacturing.

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

One independent energy economics specialist, who was not involved with the research, called the report a “highly valuable addition” after years in which parts of the automotive sector argued there was insufficient information to properly evaluate actual CO2 output.

“These findings show, beyond any doubt, that the gap between official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or diesel vehicles,” the expert stated. “Any regulatory changes concerning PHEVs should be implemented with utmost caution and considering this data.”