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Plug-in hybrid cars emit almost five times greater global warming emissions than lab-reported data show, as per a new analysis.

Widening Discrepancy Between Official and Actual Emissions

Statistics shows that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a advocacy organization. This differs significantly with lab estimates, which assumed a three-quarters decrease in emissions.

Researchers studied information from onboard energy use meters of eight hundred thousand cars registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” stated a senior researcher involved in the study. “This gap is widening and creates a serious problem. As a result, PHEVs pollute almost as heavily as petrol cars.”

Key Reasons Driving the Emissions Gap

Analysts attributed the majority of the difference to overestimates of the “utility factor” – the ratio of miles driven in battery power relative to overall mileage. The team found that only a quarter of travel was completed in electric mode, while lab assumptions suggested over four-fifths.

Even, when running in EV mode, pollution levels were well above official estimates. This happened because electric motors were not strong enough to function alone, resulting to engines burning gasoline for nearly one-third of the travel covered in electric mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV CO2 output enabled four large carmaker groups to avoid more than €5bn in fines between 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 extra per year in running costs than would be assumed under lab tests.

“The strong statements that automakers like to make about their plug-in hybrid vehicles are clearly far from the truth,” commented a transport expert. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are little improved than regular gas and diesel cars in terms of fuel use, CO₂ emissions, and running costs.”

Political Debate and Automotive Pressure

Hybrid vehicles have lately been brought back into policy discussions as automakers have pressed the EU to relax CO₂ targets. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and resistance from member states with large automotive manufacturing.

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

One external energy policy expert, who was unaffiliated with the study, called the analysis a “very useful addition” after a long period in which parts of the car industry argued there was insufficient data to accurately assess actual emissions.

“The results demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” the expert said. “All policy changes concerning PHEVs should be made with utmost care and in the light of this evidence.”