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Plug-in hybrid electric vehicles produce nearly 5x more global warming pollution than official data show, as per a recent report.

Widening Gap Between Lab and Actual CO2 Output

Data shows that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel vehicles, based on analysis conducted by a non-profit organization. This differs sharply with lab estimates, which assumed a 75% decrease in emissions.

Analysts studied information from in-vehicle energy use monitors of eight hundred thousand cars registered in the EU between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, up from three and a half times in 2021.

“Real-world emissions are rising, while official emissions are decreasing,” said a lead researcher participating in the study. “This discrepancy is widening and poses a serious issue. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric power compared to overall mileage. They found that only 27% of driving was completed in electric mode, while lab assumptions assumed 84%.

Even, when running in electric mode, pollution amounts were well above lab projections. That occurred because EV motors were insufficiently powerful enough to operate alone, leading to combustion motors burning fossil fuels for nearly a third of the distance covered in electric mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV emissions enabled several large carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay approximately €500 more per year in operating costs than would be estimated under lab conditions.

“The strong statements that manufacturers often promote about their PHEV vehicles are obviously way off the mark,” stated a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly improved than standard gas and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid vehicles have lately been brought back into political debates as automakers have pressed the EU to relax CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced intense pressure from the automotive industry and resistance from EU countries with significant car manufacturing.

Several high-level officials have suggested plug-in hybrids as a potential “flexibility” option to include in the regulation.

One independent energy economics expert, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the automotive industry claimed there was too little information to accurately assess real-world emissions.

“The results show, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or conventional vehicles,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with extreme caution and considering this evidence.”