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PHEVs produce nearly 5x more global warming emissions than lab-reported figures indicate, according to a new report.

Widening Discrepancy Between Lab and Actual CO2 Output

Statistics shows that PHEVs release only 19% less CO₂ than conventional petrol and diesel vehicles, according to research conducted by a non-profit organization. This differs significantly with lab estimates, which suggested a three-quarters reduction in pollution.

Analysts studied data from in-vehicle fuel consumption monitors of 800,000 cars sold in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while official emissions are decreasing,” said a lead researcher participating in the study. “That discrepancy is growing and creates a serious issue. As a result, PHEVs emit almost as heavily as gasoline cars.”

Key Factors Driving the Discrepancy

Researchers attributed most of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric mode compared to overall distance. They found that just a quarter of travel was completed in electric mode, while official estimates suggested 84%.

Even, when running in EV mode, pollution amounts were well above lab projections. That occurred because EV motors were not strong enough to operate independently, leading to engines burning gasoline for almost one-third of the distance completed in electric mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV CO2 output enabled four large automaker groups to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 more per year in operating costs than would be estimated under laboratory tests.

“The strong statements that automakers like to make about their PHEV cars are obviously far from the truth,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have lately been drawn again into policy debates as carmakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the car sector and opposition from member states with large automotive manufacturing.

Several senior officials have suggested plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

One independent energy policy specialist, who was unaffiliated with the research, described the analysis a “very useful contribution” after a long period in which segments of the automotive sector argued there was insufficient data to properly assess actual emissions.

“These findings demonstrate, beyond any doubt, that the difference between lab and actual PHEV energy use and CO₂ output is much, much greater than for petrol or conventional vehicles,” they said. “All regulatory changes concerning PHEVs should be implemented with utmost caution and considering that evidence.”