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Plug-in hybrid cars produce nearly five times greater global warming emissions than official data indicate, as per a recent report.

Growing Discrepancy In Official and Actual Emissions

Data shows that PHEVs emit only one-fifth lower CO₂ than conventional petrol and diesel cars, according to analysis carried out by a non-profit group. This contrasts significantly with lab tests, which assumed a 75% reduction in emissions.

Researchers studied data from in-vehicle fuel consumption meters of eight hundred thousand cars sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” said a senior researcher participating in the study. “This gap is widening and creates a serious issue. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Primary Factors Driving the Discrepancy

Researchers attributed most of the gap to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery mode relative to total mileage. They determined that just 27% of travel was completed in electric mode, while official assumptions assumed 84%.

Even, when operating in EV mode, pollution amounts were well above official projections. This happened because EV motors were insufficiently powerful sufficient to operate independently, leading to engines burning fossil fuels for nearly a third of the distance completed in electric mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions enabled four major automaker companies to avoid over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 more per year in running costs than would be assumed under lab conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are obviously way off the truth,” stated a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are helping the environment and saving costs. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Debate and Industry Pressure

Plug-in hybrid vehicles have recently been drawn again into political discussions as carmakers have pressed the EU to relax CO₂ standards. A proposed prohibition on new combustion engine vehicles in 2035 has faced intense pressure from the car industry and opposition from member states with significant car manufacturing.

Several senior officials have proposed PHEVs as a potential “compromise” solution to include in the legislation.

One external energy policy specialist, who was not involved with the research, called the analysis a “highly valuable addition” after a long period in which segments of the car sector argued there was insufficient information to accurately evaluate real-world emissions.

“These findings demonstrate, without question, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or conventional cars,” the expert stated. “All policy adjustments regarding PHEVs should be made with extreme care and in the light of this evidence.”