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PHEVs release nearly 5x more global warming emissions than official data show, according to a new analysis.

Growing Discrepancy Between Lab and Real-World Emissions

Statistics shows that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel cars, according to research conducted by a non-profit organization. That contrasts significantly with lab tests, which assumed a three-quarters decrease in emissions.

Researchers studied information from onboard fuel consumption meters of eight hundred thousand cars sold in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while official emissions are falling,” said a senior analyst participating in the study. “This discrepancy is growing and creates a serious issue. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Key Factors Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “utility factor” – the ratio of kilometers driven in electric mode compared to overall distance. The team determined that just 27% of driving was done in electric mode, while official estimates suggested over four-fifths.

Additionally, when running in electric mode, pollution amounts were significantly higher than lab estimates. That happened because electric motors were insufficiently powerful enough to operate independently, leading to engines burning fossil fuels for nearly a third of the travel covered in electric mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed several major carmaker groups to escape over €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs would pay about €500 more annually in operating expenses than is estimated under lab conditions.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are obviously far from the truth,” stated a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Political Discussion and Industry Pressure

Plug-in hybrid cars have lately been drawn back into policy discussions as carmakers have lobbied the EU to weaken CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced heavy pressure from the car industry and resistance from EU countries with large automotive industries.

Several senior officials have proposed plug-in hybrids as a possible “compromise” option to introduce in the legislation.

An independent energy economics specialist, who was unaffiliated with the study, described the report a “highly valuable addition” after a long period in which parts of the automotive industry claimed there was insufficient data to accurately assess real-world emissions.

“These findings show, without question, that the difference in official and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional vehicles,” the expert said. “All regulatory adjustments concerning PHEVs should be implemented with utmost care and considering that data.”