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Plug-in hybrid electric vehicles release nearly 5x greater global warming emissions than official data indicate, as per a new analysis.

Growing Gap In Official and Real-World Emissions

Statistics reveals that PHEVs emit just 19% lower CO₂ than traditional gas and diesel vehicles, based on analysis conducted by a non-profit group. That contrasts sharply with laboratory tests, which suggested a 75% decrease in pollution.

Researchers studied data from onboard energy use monitors of 800,000 cars registered in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” said a senior analyst participating in the report. “This discrepancy is growing and poses a significant problem. Consequently, PHEVs pollute almost as much as petrol vehicles.”

Key Factors Driving the Emissions Gap

Analysts attributed most of the difference to overestimates of the “utility factor” – the percentage of kilometers travelled in electric mode relative to total mileage. They found that only a quarter of travel was completed in EV mode, whereas lab estimates assumed over four-fifths.

Even, when running in EV mode, pollution amounts were significantly higher than official projections. This occurred because electric motors were not strong sufficient to operate independently, leading to combustion motors using fossil fuels for almost one-third of the distance covered in electric mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV emissions enabled four major automaker companies to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 extra per year in operating expenses than is assumed under lab tests.

“The bold statements that manufacturers like to make about their PHEV vehicles are clearly way off the truth,” stated a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are little better than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Policy Debate and Automotive Pressure

Hybrid cars have lately been brought back into policy debates as automakers have pressed the EU to weaken CO₂ standards. A planned prohibition on new internal combustion cars in 2035 has faced heavy pressure from the automotive industry and opposition from member states with significant automotive industries.

Some senior officials have suggested plug-in hybrids as a potential “flexibility” option to include in the regulation.

One independent energy policy specialist, who was not involved with the study, called the analysis a “highly valuable contribution” after years in which segments of the car industry claimed there was insufficient data to properly assess real-world emissions.

“These findings show, without question, that the difference in lab and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel vehicles,” they said. “Any regulatory changes regarding PHEVs should be made with utmost care and in the light of this evidence.”