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Plug-in hybrid cars produce almost five times more global warming pollution than lab-reported data show, according to a recent analysis.

Widening Discrepancy In Lab and Actual CO2 Output

Data reveals that PHEVs release just one-fifth less CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a non-profit organization. This contrasts sharply with lab tests, which assumed a three-quarters decrease in pollution.

Researchers studied information from onboard energy use meters of 800,000 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 official estimates, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are falling,” said a senior analyst participating in the report. “This gap is widening and poses a significant issue. As a result, PHEVs emit almost as much as petrol vehicles.”

Key Reasons Behind the Discrepancy

Analysts linked the majority of the gap to inflated estimates of the “utility factor” – the ratio of kilometers driven in electric power relative to total mileage. They found that just a quarter of travel was completed in electric mode, whereas official assumptions suggested 84%.

Even, when operating in EV mode, emission amounts were significantly higher than lab estimates. This happened because electric motors were insufficiently powerful enough to operate independently, leading to combustion motors burning fossil fuels for nearly one-third of the distance covered in EV mode.

Regulatory and Economic Implications

Based on estimates, the lowballing of PHEV emissions allowed four major carmaker groups to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could pay about €500 more annually in running costs than would be assumed under lab tests.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are clearly way off the truth,” stated a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are little better than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Political Debate and Automotive Lobbying

Hybrid cars have lately been brought again into political debates as carmakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced heavy pressure from the car sector and opposition from member states with large car manufacturing.

Some high-level officials have suggested plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

One external energy policy expert, who was unaffiliated with the research, described the report a “highly valuable addition” after a long period in which segments of the automotive industry claimed there was insufficient data to properly evaluate actual emissions.

“The results demonstrate, without question, that the difference between lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional vehicles,” they said. “All policy adjustments regarding PHEVs should be implemented with extreme care and considering that evidence.”