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PHEVs emit nearly 5x more planet-heating emissions than lab-reported data show, according to a recent report.

Growing Discrepancy Between Lab and Actual CO2 Output

Data shows that PHEVs release only 19% less CO₂ than traditional petrol and diesel vehicles, according to research conducted by a non-profit group. This contrasts significantly with laboratory estimates, which suggested a 75% reduction in emissions.

Analysts examined data from onboard fuel consumption meters of 800,000 cars registered in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are decreasing,” said a senior analyst participating in the report. “This discrepancy is growing and poses a significant issue. As a result, PHEVs pollute nearly as much as gasoline cars.”

Primary Factors Driving the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in electric mode compared to overall distance. The team determined that just 27% of driving was completed in electric mode, while lab assumptions suggested 84%.

Even, when operating in EV mode, pollution levels were well above lab projections. That occurred because EV motors were not strong sufficient to function alone, leading to combustion motors burning gasoline for nearly a third of the distance covered in electric mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV emissions allowed four major automaker groups to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would pay about €500 extra annually in operating costs than is estimated under lab conditions.

“The bold statements that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” commented a transport analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little better than regular gas and diesel cars in terms of energy use, CO₂ emissions, and running expenses.”

Political Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been drawn back into political discussions as automakers have pressed the European Union to relax CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced intense pressure from the automotive industry and opposition from EU countries with significant automotive manufacturing.

Some high-level politicians have suggested PHEVs as a potential “flexibility” solution to include in the regulation.

An external energy policy specialist, who was not involved with the research, described the analysis a “very useful addition” after a long period in which parts of the automotive sector argued there was too little information to accurately evaluate real-world CO2 output.

“These findings demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or diesel vehicles,” the expert said. “Any policy changes regarding PHEVs should be implemented with utmost care and considering this evidence.”