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Plug-in hybrid electric vehicles release nearly five times more planet-heating emissions than lab-reported figures indicate, as per a new report.

Growing Discrepancy Between Official and Actual Emissions

Statistics reveals that PHEVs release just 19% lower CO₂ than conventional petrol and diesel cars, based on research carried out by a advocacy group. This contrasts significantly with lab estimates, which suggested a 75% decrease in pollution.

Researchers examined data from in-vehicle fuel consumption monitors of 800,000 vehicles registered in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported figures are decreasing,” said a senior researcher participating in the report. “This gap is widening and poses a serious problem. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Primary Reasons Behind the Emissions Gap

Researchers attributed most of the gap to overestimates of the “electric driving share” – the ratio of miles driven in electric mode compared to total mileage. The team found that only 27% of driving was done in EV mode, while official estimates assumed over four-fifths.

Even, when running in EV mode, pollution amounts were significantly higher than lab projections. This happened because electric motors were not strong enough to operate independently, leading to combustion motors using gasoline for nearly one-third of the distance covered in EV mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV CO2 output allowed four major automaker companies to avoid more than €5bn in fines between 2021 and 2023, by falsely simplifying compliance with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 extra annually in operating expenses than would be assumed under laboratory tests.

“The bold statements that manufacturers often promote about their PHEV cars are clearly way off the truth,” commented a transport expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Debate and Industry Pressure

Hybrid cars have lately been brought again into political debates as automakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and resistance from member states with large car manufacturing.

Several senior politicians have suggested plug-in hybrids as a potential “compromise” option to introduce in the legislation.

One independent energy economics expert, who was not involved with the study, called the report a “highly valuable contribution” after years in which segments of the car sector claimed there was insufficient data to properly evaluate actual emissions.

“The results demonstrate, without question, that the difference between lab and real-world PHEV energy use and CO₂ emissions is significantly greater than for petrol or conventional cars,” they said. “All policy changes regarding PHEVs should be implemented with extreme care and considering this data.”