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Plug-in hybrid cars produce almost five times greater global warming emissions than official figures show, according to a recent report.

Growing Discrepancy Between Lab and Actual Emissions

Statistics reveals that PHEVs release only 19% less CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a non-profit organization. That contrasts sharply with lab estimates, which assumed a 75% reduction in pollution.

Analysts studied data from in-vehicle fuel consumption meters of eight hundred thousand vehicles registered in Europe between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are falling,” said a lead researcher participating in the report. “That gap is widening and poses a significant problem. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Primary Factors Driving the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery mode relative to total distance. The team found that just 27% of travel was done in electric mode, whereas official assumptions suggested over four-fifths.

Even, when running in electric mode, emission amounts were well above lab projections. This happened because EV motors were insufficiently powerful enough to operate independently, resulting to engines burning gasoline for almost one-third of the travel covered in electric mode.

Regulatory and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output enabled several major automaker groups to escape more than €5bn in fines from 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend about €500 more per year in operating expenses than is estimated under laboratory conditions.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are clearly far from the truth,” stated a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving money. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have recently been drawn again into policy debates as automakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and resistance from EU countries with large car manufacturing.

Some high-level politicians have proposed plug-in hybrids as a potential “compromise” option to include in the legislation.

An external energy policy specialist, who was not involved with the research, described the analysis a “very useful contribution” after years in which segments of the automotive industry argued there was too little information to accurately assess actual CO2 output.

“The results demonstrate, without question, that the gap in official and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional cars,” they stated. “Any policy changes concerning PHEVs should be made with extreme care and in the light of that evidence.”