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Plug-in hybrid cars emit nearly five times greater global warming pollution than official data indicate, as per a new report.

Widening Gap Between Lab and Real-World Emissions

Statistics reveals that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel vehicles, according to research carried out by a advocacy group. That differs sharply with laboratory estimates, which suggested a three-quarters reduction in pollution.

Researchers studied data from in-vehicle fuel consumption meters of 800,000 cars sold in the EU from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” said a senior researcher participating in the study. “That gap is widening and creates a serious issue. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in electric power relative to total distance. They determined that only 27% of driving was completed in EV mode, while lab estimates suggested over four-fifths.

Additionally, when running in EV mode, emission amounts were significantly higher than official estimates. That happened because EV motors were insufficiently powerful enough to operate alone, leading to engines using gasoline for nearly one-third of the distance covered in electric mode.

Policy and Economic Implications

According to calculations, the lowballing of PHEV CO2 output enabled several large automaker groups to avoid over €5bn in fines from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 extra annually in operating costs than is estimated under laboratory tests.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are obviously far from the mark,” commented a transport expert. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Debate and Industry Lobbying

Hybrid vehicles have lately been brought back into policy debates as carmakers have pressed the European Union to weaken CO₂ standards. A planned ban on new combustion engine cars in 2035 has faced intense lobbying from the automotive industry and resistance from member states with significant automotive manufacturing.

Several high-level officials have proposed PHEVs as a possible “compromise” option to introduce in the legislation.

An external energy policy specialist, who was not involved with the study, 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 properly assess real-world CO2 output.

“These findings show, without question, that the difference between lab and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or diesel cars,” they stated. “Any policy adjustments concerning PHEVs should be implemented with utmost care and considering this data.”